Thin-film coatings, electro-optic elements and assemblies incorporating these elements

ABSTRACT

Electro-optic elements are becoming commonplace in a number of vehicular and architectural applications. Various electro-optic element configurations provide variable transmittance and or variable reflectance for windows and mirrors. The present invention relates to various thin-film coatings, electro-optic elements and assemblies incorporating these elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/691,830 filed Jan. 22, 2010 and now published as U.S. 2010/0215903,which is a continuation-in-part of U.S. patent application Ser. No.11/713,849 filed Mar. 5, 2007 and now U.S. Pat. No. 7,688,495, whichclaims priority under 35 U.S.C. §119(e) to U.S. Provisional PatentApplications Nos. 60/779,369 filed Mar. 3, 2006; 60/810,921 filed Jun.5, 2006; 60/873,474 filed Dec. 7, 2006; and 60/888,686 filed Feb. 7,2007. The disclosure of each of the abovementioned applications isincorporated herein by reference in its entirety.

This application is related to U.S. patent applications Nos. 11/682,121filed Mar. 05, 2007 and now issued as U.S. 7,830,583 and 11/682,098filed Mar. 05, 2007 and now issued as U.S. 7,864,398. The disclosure ofeach of these applications is incorporated herein by reference in itsentirety.

BACKGROUND OF THE INVENTION

Electro-optic elements are becoming commonplace in a number of vehicularand architectural applications. Various electro-optic elementconfigurations provide variable transmittance and or variablereflectance for windows and mirrors.

The present invention relates to various thin-film coatings,electro-optic elements and assemblies incorporating these elements.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts an airplane having variable transmittance windows;

FIGS. 2 a and 2 b depict a bus and a train car, respectively, havingvariable transmittance windows;

FIG. 3 depicts a building having variable transmittance and or variablereflectivity windows;

FIG. 4 depicts a vehicle having variable transmittance windows andvariable reflectance rearview mirrors;

FIGS. 5 a-5 f depict various views of exterior rearview mirrorassemblies and related variable reflectance elements;

FIGS. 6 a-6 d depict various views of interior rearview mirrorassemblies and related variable reflectance elements;

FIG. 7 depicts a profile view of a cross section of a variablereflectance element;

FIGS. 8 a-8 d depict profile views of cross sections of variouselements;

FIGS. 9 a-9 k depict various electrical contacts for various elements;

FIG. 10 depicts an electrical control schematic for multiple elements;

FIGS. 11 a-11 d depict various electrical control schematics;

FIG. 12 depicts a graph of element wrap v. oxygen flow for various argonprocess gas pressures utilized in an element manufacturing process;

FIG. 13 depicts a graph of thin film bulk resistance v. oxygen flow forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 14 depicts a graph of thin film thickness v. oxygen flow forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 15 depicts a graph of thin film sheet resistance v. argon flow forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 16 depicts a graph of thin film bulk resistance v. argon flow forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 17 depicts a graph of thin film absorption v. oxygen flow forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 18 depicts a graph of element wrap v. oxygen flow for variousprocess gas pressures utilized in an element manufacturing process;

FIG. 19 depicts a graph of element wrap v. thin film absorption forvarious process gas pressures utilized in an element manufacturingprocess;

FIG. 20 depicts a graph of element wrap v. thin film transmittance forvarious process gas pressures utilized in an element manufacturingprocess;

FIGS. 21-32 depict various thin film surface morphologies;

FIGS. 33 a and 33 b depict thin film peak-to-peak surface roughness;

FIG. 34 depicts a graph of sputtering yield v. ion energy for variousthin film materials;

FIG. 35 depicts a graph of sputter yield v. sputter gas mass/targetmass;

FIGS. 36 and 37 depict enlarged ion-milling results;

FIG. 38 depicts a graph of thin film surface roughness v. inverse ofline speed;

FIG. 39 depicts a graph of thin film reflectance v. ion beam current;

FIG. 40 depicts a graph of thin film reflectance v. inverse of linespeed;

FIG. 41 depicts a graph of thin film b* v. inverse of line speed;

FIG. 42 depicts a graph of thin film reflectance v. ion beam residencetime;

FIG. 43 depicts a graph of thin film reflectance v. thickness;

FIG. 44 depicts a graph of thin film reflectance v. wavelength;

FIG. 45 depicts a graph of thin film transmission v. wavelength;

FIG. 46 depicts a graph of thin film reflectance v. thickness;

FIG. 47 depicts a graph of thin film transmission v. reflectance;

FIGS. 48 a-53 depict various graphs of thin film reflectance and ortransmission v. wavelength; and

FIGS. 54-62 depict various embodiments of elements having gradedthin-film coatings.

FIG. 63 illustrates an embodiment of a mirror element in accordance withthe state of the art prior to the present invention.

FIG. 64 depicts a schematic for a low cost UV blocking peripheralspectral filter coating.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1, 2 a and 2 b depict multi-passenger vehicles 102, 202 a, 202 bemploying variable transmittance windows 110, 210 a, 210 b.Multi-passenger vehicles employing variable transmittance windows 110,210 a, 210 b include, for example, aircraft 102, buses 202 a, and trains202 b. It should be appreciated that other multi-passenger vehicles,some of which are described in more detail elsewhere herein, may employvariable transmittance windows 110, 210 a, 210 b. The multi-passengervehicles generally illustrated in FIGS. 1, 2 a and 2 b also includewindow control systems (not shown in FIGS. 1-2 b, however, shown anddescribed with reference to FIG. 10) for controlling the variabletransmittance windows. Commonly assigned U.S. Pat. No. 6,567,708 andU.S. Patent Application 60/804,378, entitled Variable TransmissionWindow Systems, filed Jun. 9, 2006 describe various details related tovariable transmittance windows, the disclosures of which areincorporated herein in their entireties by reference.

Another application of variable transmittance windows is depicted inFIG. 3. Architectural windows 302 of buildings 301 may advantageouslyincorporate variable transmission functionality. It should be understoodthat these variable transmission architectural windows may be includedin residential, commercial and industrial facilities.

FIG. 4 depicts a controlled vehicle 400 comprising various variabletransmittance and variable reflectance elements. As one example, aninterior rearview mirror assembly 415 is depicted, in at least oneembodiment, the assembly 415 comprises a variable reflectance mirrorelement and an automatic vehicle exterior light control system. Detaileddescriptions of such automatic vehicle exterior light control systemsare contained in commonly assigned U.S. Pat. Nos. 5,837,994, 5,990,469,6,008,486, 6,130,448, 6,130,421, 6,049,171, 6,465,963, 6,403,942,6,587,573, 6,611,610, 6,621,616, 6,631,316 and U.S. patent applicationSer. Nos. 10/208,142, 09/799,310, 60/404,879, 60/394,583, 10/235,476,10/783,431, 10/777,468 and 09/800,460; the disclosures of which areincorporated herein in their entireties by reference. The controlledvehicle is also depicted to include a driver's side outside rearviewmirror assembly 410 a, a passenger's side outside rearview mirrorassembly 410 b, a center high mounted stop light (CHMSL) 445, A-pillars450 a, 450 b, B-pillars 455 a, 455 b and C-pillars 460 a, 460 b; itshould be understood that any of these locations may provide alternatelocations for an image sensor, image sensors or related processing and,or, control components. It should be understood that any, or all, of therearview mirrors may be automatic dimming electro-optic mirrors (i.e.variable reflectance mirror elements). In at least one embodiment, acontrolled vehicle may comprise variable transmittance windows 401, 402.The controlled vehicle is depicted to include a host of exterior lightsincluding headlights 420 a, 420 b, foil weather lights 430 a, 430 b,front turn indicator/hazard lights 435 a, 435 b, tail lights 425 a, 425b, rear turn indicator lights 426 a, 426 b, rear hazard lights 427 a,427 b and backup lights 440 a, 440 b. It should be understood thatadditional exterior lights may be provided, such as, separate low beamand high beam headlights, integrated lights that comprise multipurposelighting, etc. It should also be understood that any of the exteriorlights may be provided with positioners (not shown) to adjust theassociated primary optical axis of the given exterior light. In at leastone embodiment, at least one exterior mirror assembly is provided withpivoting mechanisms to allow pivoting in directions 410 a 1, 410 a 2,410 b 1, 410 b 2. It should be understood that the controlled vehicle ofFIG. 4 is generally for illustrative purposes and that suitableautomatic dimming rearview mirrors, such as those disclosed in thepatents and patent applications incorporated herein by reference, may beemployed along with other features described herein and withindisclosures incorporated herein by reference.

Preferably, the controlled vehicle comprises an inside rearview mirrorof unit magnification. Unit magnification mirror, as used herein, meansa plane or flat mirror with a reflective surface through which theangular height and width of an image of an object is equal to theangular height and width of the object when viewed directly at the samedistance with the exception for flaws that do not exceed normalmanufacturing tolerances. A prismatic day-night adjustment rearviewmirror wherein at least one associated position provides unitmagnification is considered herein to be a unit magnification mirror.Preferably, the mirror provides a field of view with an includedhorizontal angle measured from the projected eye point of at least 20degrees and a sufficient vertical angle to provide a view of a levelroad surface extending to the horizon beginning at a point not greaterthan 61 m to the rear of the controlled vehicle when the controlledvehicle is occupied by a driver and four passengers or the designatedoccupant capacity, if less, based on an average occupant weight of 68kg. It should be understood that the line of sight may be partiallyobscured by seated occupants or by head restraints. The location of thedriver's eye reference points are preferably in accordance withregulation or a nominal location appropriate for any 95th percentilemale driver. In at least one embodiment the controlled vehicle comprisesat least one outside mirror of unit magnification. Preferably, theoutside mirror provides a driver of a controlled vehicle a view of alevel road surface extending to the horizon from a line, perpendicularto a longitudinal plane tangent to the driver's side of the controlledvehicle at the widest point, extending 2.4 m out from the tangent plane10.7 m behind the driver's eyes, with the seat in the rearmost position.It should be understood that the line of sight may be partially obscuredby rear body or fender contours of the controlled vehicle. Preferably,the locations of the driver's eye reference points are in accordancewith regulation or a nominal location appropriate for any 95thpercentile male driver. Preferably, the passenger's side mirror is notobscured by an unwiped portion of a corresponding windshield and ispreferably adjustable by tilting in both horizontal and verticaldirections from the driver's seated position. In at least oneembodiment, the controlled vehicle comprises a convex mirror installedon the passenger's side. Preferably, the mirror is configured foradjustment by tilting in both horizontal and vertical directions.Preferable, each outside mirror comprises not less than 126 cm ofreflective surface and is located so as to provide the driver a view tothe rear along an associated side of the controlled vehicle. Preferably,the average reflectance of any mirror, as determined in accordance withSAE Recommended Practice J964, OCT84, is at least 35 percent (40% formany European Countries). In embodiments where the mirror element iscapable of multiple reflectance levels, such as with electro-opticmirror elements in accordance with the present invention, the minimumreflectance level in the day mode shall be at least 35 (40 when forEuropean use) percent and the minimum reflectance level in the nightmode shall be at least 4 percent. It should be understood that variousembodiments of the present invention are equally applicable formotorcycle windscreens and rearview mirrors.

Turning now to FIGS. 5 a and 5 b, various components of an outsiderearview mirror assembly 510 a, 510 b are depicted. As described indetail herein, an electro-optic mirror element may comprise a firstsubstrate 521 b secured in a spaced apart relationship with a secondsubstrate 522 b via a primary seal 523 b to form a chamber therebetween. In at least one embodiment, at least a portion of the primaryseal is left void to form at least one chamber fill port 523 b 1. Anelectro-optic medium is enclosed in the chamber and the fill port(s) aresealingly closed via a plug material 523 b 2. Preferably, the plugmaterial is a UV curable epoxy or acrylic material. In at least oneembodiment a spectral filter material 545 a, 545 b is located proximatea second surface of a first substrate, near the periphery of the mirrorelement. Electrical connectors 525 b 1, 525 b 2 are preferably securedto the element, respectively, via first adhesive material 526 b 1, 526 b2. The mirror element is secured to a carrier plate 575 b via secondadhesive material 570 b. Electrical connections from the outsiderearview mirror to other components of the controlled vehicle arepreferably made via a connecter 585 b. The carrier is attached to anassociated housing mount 585 b via a positioner 580 b. Preferably, thehousing mount is engaged with a housing 515 a, 515 b and secured via atleast one fastener 534 b 4. Preferably the housing mount comprises aswivel portion configured to engage a swivel mount 533 b. The swivelmount is preferably configured to engage a vehicle mount 530 b via atleast one fastener 531 b. Additional details of these components,additional components, their interconnections and operation is providedherein.

With further reference to FIGS. 5 a and 5 b, an outside rearview mirrorassembly 510 a is oriented such that a view of the first substrate 521 bis shown with a spectral filter material 524 b positioned between theviewer and the primary seal material 523 b. A blind spot indicator 550a, a keyhole illuminator 555 a, a puddle light 560 a, a supplementalturn signal 540 a, or 541 a, a photo sensor 565 a, anyone thereof, asubcombination thereof or a combination thereof may be incorporatedwithin the rearview mirror assembly such that they are positioned behindthe element with respect to the viewer. Preferably, the devices 550 a,555 a, 560 a, 540 a, or 541 a, 565 a are configured in combination withthe mirror element to be at least partially covert as discussed indetail herein and within various references incorporated by referenceherein. Additional details of these components, additional components,their interconnections and operation are provided herein.

Turning now to FIGS. 5 c-5 e, a discussion of additional features inaccordance with the present invention is provided. FIG. 5 c depicts arearview mirror element 500 c viewed from the first substrate 502 c witha spectral filter material 596 c positioned between the viewer and aprimary seal material 578 c. A first separation area 540 c is providedto substantially electrically insulate a first conductive portion 508 cfrom a second conductive portion 530 c. A perimeter material 560 c isapplied to the edge of the element. FIG. 5 d depicts a rearview mirrorelement 500 d viewed from the second substrate 512 d with a primary sealmaterial 578 d positioned between the viewer and a spectral filtermaterial 596 d. A second separation area 586 d is provided tosubstantially electrically insulate a third conductive portion 518 dfrom a fourth conductive portion 587 d. A perimeter material 560 d isapplied to the edge of the element. FIG. 5 e depicts a rearview mirrorelement 500 e viewed from a section line FIG. 5 e-FIG. 5 e of either theelement of FIG. 5 c or 5 d. A first substrate 502 e is shown to besecured in a spaced apart relation via a primary seal material 578 ewith a second substrate 512 e. A spectral filter material (in at leastone embodiment referred to herein as “chrome ring”) 596 e is positionedbetween a viewer and the primary seal material 578 e. First and secondelectrical clips 563 e, 584 e, respectively, are provided to facilitateelectrical connection to the element. A perimeter material 560 e isapplied to the edge of the element. It should be understood that theprimary seal material may be applied by means commonly used in the LCDindustry such as by silk-screening or dispensing. U.S. Pat. No.4,094,058, to Yasutake et al., the disclosure of which is incorporatedin its entirety herein by reference, describes applicable methods. Usingthese techniques the primary seal material can be applied to anindividually cut to shape substrate or it can be applied as multipleprimary seal shapes on a large substrate. The large substrate withmultiple primary seals applied may then be laminated to another largesubstrate and the individual mirror shapes may be cut out of thelaminate after at least partially curing the primary seal material. Thismultiple processing technique is a commonly used method formanufacturing LCD's and is sometimes referred to as an array process.Electro-optic devices in accordance with the present invention may bemade using a similar process. All coatings such as the transparentconductors, reflectors, spectral filters and in the case of solid stateelectro-optic devices the electro-optic layer or layers may be appliedto a large substrate and patterned if necessary. The coatings may bepatterned using a number of techniques such as by applying the coatingsthrough a mask, by selectively applying a patterned soluble layer underthe coating and removing it and the coating on top of it after coatingapplication, laser ablation or etching. These patterns may containregistration marks or targets used to accurately align or position thesubstrates throughout the manufacturing process. This is usually doneoptically for instance with a vision system using pattern recognitiontechnology. The registration marks or targets may also be applied to theglass directly such as by sand blasting, laser or diamond scribing ifdesired. Spacing media for controlling the spacing between the laminatedsubstrates may be placed into the primary seal material or applied to asubstrate prior to lamination. The spacing media or means may be appliedto areas of the laminate that will be cut away from the finishedsingulated mirror assemblies. The laminated arrays can be cut to shapebefore or after filling with electro-optic material and plugging thefill port if the devices are solution phase electro-optic mirrorelements.

Turning now to FIGS. 6 a and 6 b, there is shown an inside rearviewmirror assembly 610 a, 610 b as viewed looking at the first substrate622 a, 622 b with a spectral filter material 645 a or a bezel 645 bpositioned between a viewer and a primary seal material (not shown). Themirror element is shown to be positioned within a movable housing 675 a,675 b and optionally combined with a stationary housing 677 a on amounting structure 681 a (w/stationary housing) or 681 b (w/o stationaryhousing). A first indicator 686 a, a second indicator 687 a, operatorinterfaces 691 a, 691 b and a first photo sensor 696 a are positioned ina chin portion of the movable housing. A first information display 688a, 688 b, a second information display 689 a and a second photo sensor697 a are incorporated within the assembly such that they are behind theelement with respect to the viewer. As described with regard to theoutside rearview mirror assembly, it is preferable to have devices 688a, 688 b, 689 a, 697 a at least partially covert as described in detailherein. In at least one embodiment an interior rearview mirror assemblymay comprise at least one or more illumination assemblies 670 b atprinted circuit board 665 b, at least one microphone, a sub-combinationthereof, a combination thereof, or other combinations along withaforementioned devices. It should be understood that aspects of thepresent invention may be individually or collectively incorporated inelectro-optic windows or mirrors in a multitude of combinations.

FIG. 6 c depicts a plan view of a second substrate 612 c comprising astack of materials on a third, fourth or both third and fourth surfaces.In at least one embodiment, at least a portion 620 c 1 of a stack ofmaterials, or at least the substantially opaque layers of a stack ofmaterials, are removed, or masked, beneath the primary seal material. Atleast a portion 620 c 2 of at least a layer of the stack of materialsextends substantially to the outer edge of the substrate or extends toan area to facilitate electrical contact between the third surface stackand an element drive circuit (not shown in FIG. 6 c). Relatedembodiments provide for inspection of the seal and or plug viewing andor plug curing from the rear of the mirror or window element subsequentto element assembly. In at least one embodiment, at least a portion ofan outer edge 620 c 1 of a stack of materials 620 c is located betweenan outer edge 678 c 1 and an inner edge 678 c 2 of a primary sealmaterial 678 c. In at least one embodiment, the portion 620 c 1 of astack of materials, or at least the substantially opaque layers of astack of materials, are removed, or masked, beneath the primary sealmaterial between approximately 2 mm and approximately 8 mm wide,preferably approximately 5 mm wide. At least a portion 620 c 2 of atleast a layer of the stack of materials extends substantially to theouter edge of the substrate or extends to an area to facilitateelectrical contact between the third surface stack and an element drivecircuit (not shown) between approximately 0.5 mm and approximately 5 mmwide, preferably approximately 1 mm. It should be understood that any ofthe first, second, third and fourth surface layers or stacks ofmaterials may be as disclosed herein or within the referencesincorporated elsewhere herein by reference.

FIG. 6 d depicts a plan view of a second substrate 612 d comprising athird surface stack of materials. In at least one embodiment, at least aportion of an outer edge 620 d 1 of a third surface stack of materials620 d is located between an outer edge 678 d 1 and an inner edge 678 d 2of a primary seal material 678 d. In at least one related embodiment, aconductive tab portion 682 d extends from an edge of the secondsubstrate inboard of an outer edge 678 d 1 of a primary seal material678 d. In at least one related embodiment, a conductive tab portion 682d 1 overlaps with at least a portion of a third surface stack ofmaterials beneath a primary seal material 678 d. In at least oneembodiment, a substantially transparent conductive layer (not shownindividually), such as a conductive metal oxide, of a third surfacestack of materials extends beyond an outer edge 620 d 1 of a remainderof the third surface stack as depicted in FIG. 8 b to provide externalelectrical connection to the third surface. It should be understood thata conductive tab may be deposited along any of the substrate peripheralareas as shown in FIGS. 9 c-9 i. In at least one embodiment, aconductive tab portion comprises chrome. It should be understood thatthe conductive tab portion improves conductivity over the conductiveelectrode; as long as a conductive electrode layer is provided withsufficient conductivity, the conductive tab portion is optional. In atleast one embodiment, the conductive electrode layer imparts the desiredcolor specific characteristics of the corresponding reflected light raysin addition to providing the desired conductivity. Therefore, when theconductive electrode is omitted, color characteristics are controlledvia the underlayer material specifications. It should be understood thatany of the first, second, third and fourth surface layers or stacks ofmaterials may be as disclosed herein or within the referencesincorporated elsewhere herein by reference.

FIG. 7 depicts rearview mirror element 700 which is an enlarged view ofthe element depicted in FIG. 5 e to provide greater detail. Element 700comprises a first substrate 702 having a first surface 704 and a secondsurface 706. A first conductive electrode portion 708 and a secondconductive electrode portion 730 applied to the second surface 706 aresubstantially electrically insulated from one another via a firstseparation area 740. As can be seen, in at least one embodiment theseparation area is located such that the spectral filter material 796and a corresponding adhesion promotion material 793 are alsosubstantially electrically insulated to define first and second spectralfilter material portions 724, 736, respectively, and first and secondadhesion promotion material portions 727, 739, respectively. A portionof the first separation area 740, 540 c, 540 d, 540 e is shown to beextending parallel within a portion of the primary seal material 778located near the center thereof. It should be understood that thisportion of the separation area 740 may lie such that a viewer would notreadily perceive a line within the spectral filter material; forexample, a portion of the separation area may be substantially alignedwith an inboard edge 797 of spectral filter material 596. It should beunderstood that when any portion of the separation area 740 is locatedinboard of the primary seal material, as is described in more detailelsewhere herein, a discontinuity in the electro-optic material coloringand, or, clearing may be observed. This operational characteristic maybe manipulated to derive a subjectively visually appealing element.

With further reference to FIG. 7, the element 700 is depicted tocomprise a second substrate 712 having a third surface 715 and a fourthsurface 714. It should be noted that the first substrate may be largerthan the second substrate to create an offset along at least a portionof the perimeter of the mirror. Third and fourth conductive electrodeportions 718, 787, respectively, are shown proximate the third surface715 substantially electrically insulated via second separation area 786.A portion of the second separation area 786, 586 c, 586 d, 586 e isshown to be extending parallel within a portion of the primary sealmaterial 778 located near the center thereof. It should be understoodthat this portion of the separation area 786 may lie such that a viewerwould not readily perceive a line within the spectral filter material;for example, a portion of the separation area may be substantiallyaligned with an inboard edge 797 of spectral filter material 796. Asfurther shown in FIG. 7, a reflective material 720 may be appliedbetween an optional overcoat material 722 and the third conductiveelectrode portion 718. It should be understood that any of the materialsas disclosed in commonly assigned U.S. Pat. Nos. 6,111,684, 6,166,848,6,356,376, 6,441,943, 10/115,860 5,825,527, 6,111,683, 6,193,378,09/602,919, 10/260,741, 60/873,474 and 10/430,885, the disclosures ofwhich are incorporated herein by reference, may be employed to define aunitary surface coating, such as a hydrophilic coating on a firstsurface, or a composite stack of coatings, such as conductive electrodematerial, spectral filter material, adhesion promotion material,reflective material, overcoat material applied to the first, second,third and fourth surfaces. It should be additionally understood that ahydrophobic coating, such as, a fluorinated alkyl saline or polymer, asilicone containing coating or a specially textured surface may beapplied to the first surface. Either a hydrophilic or hydrophobiccoating will alter the contact angle of moisture impinging upon thefirst surface relative to glass with no such coating and will enhancerear vision when moisture is present. It should be understood that boththird surface and fourth surface reflector embodiments are within thescope of the present invention. In at least one embodiment, thematerials applied to the third surface and, or, fourth surface areconfigured to provide a partially reflective/partially transmissivecharacteristic for at least a portion of the corresponding surfacestack. In at least one embodiment, the materials applied to the thirdsurface are integrated to provide a combination reflector/conductiveelectrode. It should be understood that additional “third surface”materials may extend outboard of the primary seal, in which case, itshould be understood that the corresponding separation area extendthrough the additional materials. Having at least a portion of theprimary seal visible from the fourth surface, as depicted in FIG. 6 cfor example, facilitates inspection and UV curing of plug material. Inat least one embodiment, at least a portion of a stack of materials 620c, or at least the substantially opaque layers of a stack of materials,are removed, or masked, beneath the primary seal material to provide forinspection of at least 25% of the primary seal width around at least aportion of the perimeter. It is more preferred to provide for inspectionof 50% of the primary seal width around at least a portion of theperimeter. It is most preferred to provide for inspection of at least75% of the primary seal width around at least a portion of theperimeter. Various embodiments of the present invention will incorporateportions of a particular surface having a coating or stack of coatingsdifferent from other portions; for example, a “window” in front of alight source, information display, a photo sensor, or a combinationthereof may be formed to selectively transmit a particular band of lightray wavelengths or bands of light ray wavelengths as described in manyof the references incorporated herein.

With further reference to FIGS. 6 a-6 b and 7, the first separation area740 cooperates with a portion of the primary seal material 775 to definethe second conductive electrode portion 730, the second spectral filtermaterial portion 736 and the second adhesion promotion material portion739 substantially electrically insulated from the first conductiveelectrode portion 708, the first spectral filter material portion 724and first adhesion promotion material portion 727. This configurationallows for placement of an electrically conductive material 748 suchthat the first electrical clip 763 is in electrical communication withthe third conductive electrode portion 718, the reflective material 720,the optional overcoat 722 and the electro-optic medium 710. It should beapparent, particularly in embodiments wherein the electricallyconductive material 748 is applied to the element prior to placement ofthe first electrical clip 769, that electrically conductive material mayat least partially separate the interfaces 757, 766, 772, 775.Preferably, the material, or composition of materials, forming the thirdconductive electrode portion 718, the first electrical clip 763 and theelectrically conductive material 748 are chosen to promote durableelectrical communication between the clip and the materials leading tothe electro-optic medium. The second separation area 786 cooperates witha portion of the primary seal material 775 to define the fourthconductive electrode portion 787 substantially electrically insulatedfrom the third conductive electrode portion 718, the reflective layer720, the optional overcoat material 722 and the electro-optic medium710. This configuration allows for placement of an electricallyconductive material 790 such that the second electrical clip 784 is inelectrical communication with the first adhesion promotion materialportion 727, the first spectral filter material portion 724, the firstconductive electrode portion 708 and the electro-optic medium 710. Itshould be apparent, particularly in embodiments wherein the electricallyconductive material 790 is applied to the element prior to placement ofthe first electrical clip 784, that electrically conductive material mayat least partially separate the interfaces 785, 788, 789. Preferably,the material, or composition of materials, forming the first conductiveelectrode portion 708, the first electrical clip 784, the adhesionpromotion material 793, the spectral filter material 796 and theelectrically conductive material 790 are chosen to promote durableelectrical communication between the clip and the materials leading tothe electro-optic medium.

It is sometimes desirable to provide one or more optional flashover-coat layers 722 over reflective layer 720, such that it (and notthe reflective layer 720) contacts the electrochromic medium. This flashover-coat layer 722 must have stable behavior as an electrode, it musthave good shelf life, it must bond well to the reflective layer 720, andmaintain this bond when the seal member 778 is bonded thereto. Ifoptical properties from the underlayer(s) are to be visible the coverlayer it must be sufficiently thin, such that it does not completelyblock the reflectivity of layer(s) beneath 720. In accordance withanother embodiment of the present invention, when a very thin flashover-coat 722 is placed over the highly reflecting layer, then thereflective layer 720 may be silver metal or a silver alloy because theflash layer protects the reflective layer while still allowing thehighly reflecting layer 720 to contribute to the reflectivity of themirror. In such cases, a thin (e.g., less than about 300 Angstroms, andmore preferably less than about 100 Angstroms) layer of rhodium,ruthenium, palladium, platinum, nickel, tungsten, molybdenum or theiralloys, is deposited over the reflective layer 720. The thickness of theflash layer is dependent on the material selected. For example, elementsconstructed with a third surface coating of chrome under ruthenium underrhodium under silver coated with a flash layer of as little as 10Angstroms of ruthenium showed improved resistance compared to elementswithout the flash layer both to the formation of spot defects duringprocessing and haze in the viewing area of the element when subjected tohigh temperature testing. The initial reflectivity of the elements withthe ruthenium flash layer was 70-72%. When reflective layer 720 issilver, flash layer 722 may also be a silver alloy or an aluminum-dopedzinc oxide. The flash layer or a thicker cover layer may also be atransparent conductor such as a transparent metal oxide. Cover layer(s)may be chosen specifically to compliment the other layers for suchfactors as barrier properties, advantageous interferential optics,balancing of compressive or tensile stresses and the like. It should beunderstood that the flash layer as described above may be used in otherembodiments described elsewhere in this document.

such cover layers when made from the aforementioned list of metals orother metals/alloys/semi-metals found to be compatible with theelectrochromic system, when the metal or semi-metal layer(s) is thickerthan 300 Angstroms tend to allow little optical effect from the layersbeneath it. If it is considered more desirable that the appearance ofthe metallic cover layer it may be advantageous to use such a thickercover layer. Some description of such stacks is provided in commonlyassigned European patent EP0728618A2 “Dimmable Rearview Mirror for MotorVehicles” Bauer, et al., which is hereby incorporated by reference. Whensuch thicker cover layer(s), which could be used in combination withglue layers and flash layers, and transparent conductive layers, such asindium doped tin oxide, aluminum doped zinc oxide, or indium zinc oxideare used, the conductivity benefits of having underlayers such assilver, silver alloys, copper, copper alloys, aluminum or aluminumalloys, would still be present. Layers typically thought of asinsulators such as titanium dioxide, silicon dioxide, zinc sulfide orthe like, may also be utilized in such a cover layer stack orinterlayers and not negate the benefits of the more highly conductivelayer(s) as long as their layer thicknesses were such that they stillpassed sufficient current from the more highly conductive layers.

It is known in the electrochromic art that a mirror or window may notdarken uniformly when an electrical potential is applied to the element.The non-uniform darkening results from local differences in electricalpotential across the solid state EC materials, fluid or gel in an ECelement. The electrical potential across the element varies with thesheet resistance of the electrodes, the bus bar configuration, theconductivity of the EC medium, the concentration of the EC medium, thecell spacing or distance between the electrodes, and the distances fromthe bus bars. A commonly proposed solution to this problem is to makethe coatings or layers composing the electrodes thicker thus reducingtheir sheet resistance and enabling a faster darkening element. As willbe discussed below there are practical penalties that are imparted thatrestrict this simplistic approach to solving the problem. In manyinstances the penalties make an EC element unsuitable for a givenapplication. In at least one embodiment of the present inventionimproved electrode materials, methods of manufacturing said electrodesand bus bar configurations are described that solve problems that arisewith simply thickening the electrode layers and result in EC elementswith faster, more uniform darkening characteristics.

In a typical inside mirror the bus bars run parallel to the longdimension. This is to minimize the potential drop across the partbetween the electrodes. The mirror also typically consists of a highsheet resistance transparent electrode and a lower sheet resistancereflector electrode. The mirror will darken most quickly near the busbar for the higher sheet resistance electrode and slowest at someintermediate position between the two electrodes. Near the bus bar forthe lower sheet resistance electrode will have a darkening rate betweenthese two values. There is a variation in effective electrical potentialas one moves between the two bus bars. In the case of two long parallelbus bars that have a relatively short distance between them (distancebetween the bus bars is less than half the length of the bus bars) themirror will darken in a “window shade” fashion. This means that themirror darkens faster near one bus and the darkening appears to movebetween the two bus bars in a gradual fashion. Typically, the darkeningrate is measured at the middle of the part and in the case of a mirrorwith a width to height ratio greater than 2, any non-uniformities indarkening rate are relatively minor.

As the size of the mirrors increases, and along with it the distancebetween the bus bars, the relative difference in the darkening rateacross the parts also increases. This can be exacerbated when themirrors are designed for an outside application. The metals that canwithstand the rigors of such an environment typically have lowerconductivity than metals such as silver or silver alloys that aresuitable and common for inside mirror applications. A metal electrodefor an outside application may therefore have a sheet resistance up to 6ohms/sq while an inside mirror may have a sheet resistance of <0.5ohms/sq. In other outside mirror applications the transparent electrodemay be limited in thickness for various optical requirements. Thetransparent electrode, such as ITO, is often limited to a ½ wavethickness in the most common usage. This limitation is due to propertiesof the ITO discussed herein but also due to the expense associated withmaking an ITO coating thicker. In other applications the coating islimited to 80% of the ½ wave thickness. Both of these thicknessconstraints limit the sheet resistance of the transparent electrode togreater than about 12 ohm/sq for a ½ wave and up to 17-18 ohms/sq for acoating that is 80% of a ½ wave coating. The higher sheet resistance ofthe metal and transparent electrodes results in a slower, less uniformdarkening mirror.

The darkening rate may be estimated from an analysis of the EC elementin terms of an electrical circuit. The discussion below pertains tocoatings that have uniform sheet resistance across the element. Thepotential at any location between parallel electrodes is simply afunction of the sheet resistance of each electrode and the resistance ofthe EC medium. In Table 1 below the average potential across the elementbetween the electrodes is presented along with the difference betweenthe maximum and minimum potential. This example is for an element with a10 cm spacing between the parallel bus bars, a 180 micron cell spacing,a 1.2 volt driving voltage and 100,000 Ohm*cm fluid resistivity. Sixcombinations of top and bottom electrode sheet resistance are compared.

TABLE 1 Ex: 1 Ex: 2 Ex: 3 Ex: 4 Ex: 5 Ex: 6 Top Plate Sheet Resistance17 17 12 12 9 9 (ohm/sq) Bottom Plate Sheet Resistance 5 0.5 5 0.5 5 0.5(ohm/sq) Distance Between Electrodes (cm) 10 10 10 10 10 10 Cell Spacing(um) 180 180 180 180 180 180 Fluid Resistivity (Ohm * cm) 100000 100000100000 100000 100000 100000 Driving Potential (V) 1.2 1.2 1.2 1.2 1.21.2 Finite Element Width (cm) 1 1 1 1 1 1 Potential at Anode (V) 1.1681.197 1.168 1.197 1.168 1.197 Potential at Cathode (V) 1.096 1.096 1.1251.125 1.143 1.143 Average Potential (V) 1.131 1.145 1.146 1.160 1.1551.169

The speed of darkening is fastest at the electrical contact to thehighest sheet resistance electrode and is related to the effectivepotential at this position. The higher the effective potential adjacentto this electrical contact (or elsewhere) the faster the averagedarkening of the mirror will be. The fastest overall darkening time willoccur when the potential is as high as possible across the part. Thiswill drive the electrochemistry to darken at an accelerated rate. Thesheet resistance of the coatings on both the top and bottom substratesplays a role in determining the effective potential between theelectrodes, but as can be seen from the table the high sheet resistanceelectrode plays a more critical role. In past electrochromic art theimprovements were driven almost exclusively by lowering the sheetresistance of the low resistance electrode. This was because the use ofmaterials such as silver gave substantive benefits and was relativelyeasy to implement.

It is known in the art that the overall rate can be increased as thedriving potential is increased but the trends will be constantindependent of the driving voltage. It is also known that the currentdraw at a given voltage influences the darkening uniformity. Uniformitycan be improved by adjustments to cell spacing, concentration, or choiceof EC materials, but often improvements in uniformity using theseadjustments can have a negative impact on darkening speed, clearingspeed or both darkening and clearing speed. For example, increasing cellspacing and decreasing fluid concentration will decrease the currentdraw and will thereby improve uniformity, but the clearing time willincrease. Therefore, the sheet resistance of the layers must beappropriately set to attain both speed of darkening and uniformity ofdarkening. Preferably the sheet resistance of the transparent electrodeshould be less than 11.5 ohms/sq, preferably less than 10.5 ohms/sq andmore preferably less than 9.5 ohms/sq and due to the opticalrequirements discussed below, in some embodiments, the thickness of thetransparent electrode should be less than about a half wave opticalthickness. The reflector electrode should be less than about 3 ohms/sq,preferably less than about 2 ohms/sq and most preferably less than 1ohm/sq. A mirror or EC element so constructed will also have arelatively uniform darkening such that the difference in darkening timebetween the fastest and slowest darkening rate is less than a factor of3, preferably less than a factor of 2 and most preferably less than afactor of 1.5. Novel, high-performance, low-cost materials are discussedbelow that enable these fast, uniform darkening elements.

In other applications it may be impractical to have two relativelyparallel bus bars. This may be due to an uneven shape common withoutside mirrors. In other circumstance it may be desirable to have apoint contact to the low resistance electrode. The point contact mayenable the minimization or elimination of the laser deletion line usedin some applications. The use of a point contact simplifies or ispreferential for some aspects of the mirror construction but it makes itdifficult to achieve a relative uniform potential across the part. Theelimination of the relatively long bus along the low resistancereflector electrode effectively increases the resistance of theelectrode. Therefore, novel combinations of bus bars and coating sheetresistance values are needed to attain fast, uniform darkening.

As noted above one skilled in the art would have anticipated that itwould require extremely low sheet resistance values on the metalreflector electrode to enable a point contact scheme. Unexpectedly itwas discovered that it is necessary to have a lower sheet resistance forthe transparent electrode to improve the uniformity. Table 2 shows theresults of the uniformity experiments. In this test we made solutionphase EC elements that were approximately 8 inches wide by 6 inchestall. The benefits of element designs discussed herein pertainpredominantly to large elements. A large element is defined as one thathas the minimum distance from the edge of any point on the edge of theviewing area to the geometric center is greater than approximately 5 cm.Lack of uniform darkening becomes even more problematic when thedistance is greater than approximately 7.5 cm and even more problematicwhen the distance is greater than approximately 10 cm. The sheetresistance of the transparent electrode (ITO) and the metal reflectorwere varied as noted in Table 2. Contact was made to the metal electrodewith a point contact. A clip contact such as the so called J-clip wasused with an Ag paste line approximately 1″ long to provide electricalcontact to the metal reflector along one of the short length sides ofthe mirror. Electrical contact was made to the transparent electrode viaan Ag paste along the one side opposite the point contact and continuingdown one third of the distance along both long sides of the mirror. Thedarkening time (T5515) was measured at three locations on the mirror.Position 1 is near the point contact, position 2 is at the edge of thetransparent electrode bus opposite the point contact and position 3 isat the center of the mirror. The T5515 time (in seconds) is the time ittakes the mirror to go from 55% reflectance to 15% reflectance. The maxreflectance is the maximum reflectance of the mirror. The delta T5515 isthe time difference between either point 1 and point 2 or between point2 and point 3. This is a measure of the difference in darkening ratebetween the fastest position and the other two locations on the mirror.As the darkening becomes more uniform these numbers become closertogether. The timing factor is the darkening time at a given positiondivided by the time at the fastest position. This shows the relativescaling of time between the different locations independent of theabsolute rate at any given location. As noted above, it is preferred tohave a timing factor less than 3 and preferable less than 2 and mostpreferably less than 1.5. It can be seen from Table 2 that we do notattain a timing factor of 3 when the ITO sheet resistance is at 14ohms/sq for this particular mirror configuration. All three exampleswith an ITO with 9 ohms per square have timing factors less than 3. Thecenter of mirror reading is the location that deviates most from thefastest location. A statistical analysis was conducted on this datawhich revealed unexpectedly that the ITO sheet resistance was the solefactor that contributed to the timing factor. Using the statisticalmodels an ITO sheet resistance of less than about 11.5 ohms/sq is neededto have a timing factor of 3.0 or less for this embodiment. Using thesame statistical models the ITO must have a sheet resistance of lessthan 7 ohms/sq for the timing factor to be less than 2.0 for this mirrorconfiguration. Even though the timing factor is not affected by thesheet resistance of the third surface reflector the overall darkeningrate is affected. When the sheet resistance of said reflector is lessthan or equal to 2 ohms/sq and the ITO is at approximately 9 ohms/sq thedarkening rate for this mirror is less than 8 seconds in the center.This value corresponds approximately to a mirror of similar size with aconventional bus arrangement. Therefore, by lowering the sheetresistance of the ITO a point contact is enabled with a relatively highsheet resistance reflector.

TABLE 2 ITO Measure- Reflector ohm/ ment Max delta timing ohms/sq sqPosition Reflectance T5515 T5515 factor 0.5 9 1 55.3 3.7 1.3 1.6 0.5 9 255.5 2.3 0.5 9 3 55.3 6.0 3.7 2.6 1 9 1 56.0 5.4 2.3 1.7 1 9 2 56.0 3.11 9 3 56.0 7.2 4.1 2.3 2 9 1 55.8 5.0 1.9 1.6 2 9 2 55.9 3.1 2 9 3 55.97.8 4.6 2.5 0.5 14 1 56.5 5.6 2.8 2.0 0.5 14 2 56.6 2.9 0.5 14 3 56.510.2 7.3 3.6 1 14 1 57.6 6.8 3.4 2.0 1 14 2 57.6 3.4 1 14 3 57.5 12.28.8 3.6 2 14 1 57.3 8.4 4.4 2.1 2 14 2 57.5 4.0 2 14 3 57.4 14.0 9.9 3.5

The unexpected role of the sheet resistance of the ITO in the uniformityand speed of darkening was expanded on in another set of experiments. Inthese experiments the length of bus bar contact to the higher sheetresistance electrode, in this example ITO, was extended further down thesides of the mirror and even onto the bottom edge of the mirror in somecases. Table 3 demonstrates the effect on uniformity with changes in buslength. In these tests the element shape and configuration are the sameas for Table 2 except where noted. The contact percentage is apercentage comparison of the bus bar length of the ITO contact comparedto the total length of the perimeter. The bus bar ratio is the length ofthe ITO contact relative to the small reflector contact of approximately2 cm or less.

The data from Table 3 depicts that increasing the bus length of thehigher sheet resistance electrode significantly improves uniformity ofdarkening. For the 2 ohm/sq. reflector, increasing the length of the buscontact from 40% to 85% improves the timing factor from 2.4 to 1.7. Forthe 0.5 ohm/sq reflector, the same change in ITO bus length from 40 to85% improves the timing factor from 3.2 to 1.2 and significantlyimproves the darkening rate. It is noted that the element with the lowersheet resistance reflector is generally faster to darken than thecomparable 2 ohm/sq. case, but the uniformity of the 0.5 ohm case with ashorter ITO contact is actually worse as demonstrated by the timingfactor. The increase bus length to the ITO is particularly helpful forthe element with the 0.5 ohm/sq. reflector.

When the contact percentage is increased, the position of the fastestand slowest darkening can change as well. In this example higher contactpercentage significantly improves the darkening times at both positions1 and 3 and the corresponding timing factors.

TABLE 3 Contact Bus Bar Reflector ITO Measurement Max delta timingPercentage Ratio ohms/sq ohm/sq Position Reflectance T5515 T5515 factor85 20 2 9 1 57.0 2.9 85 20 2 9 2 57.0 3.7 0.8 1.3 85 20 2 9 3 57.3 4.81.9 1.7 58 13 2 9 1 56.6 3.4 58 13 2 9 2 57.2 3.5 2.2 1.0 58 13 2 9 357.5 5.6 2.2 1.6 40 9 2 9 1 56.9 8 4.6 2.4 40 9 2 9 2 57.3 3.4 40 9 2 93 57.4 8.2 4.8 2.4 85 20 0.5 9 1 56.0 3 85 20 0.5 9 2 56.2 3 85 20 0.5 93 56.1 3.5 0.5 1.2 58 13 0.5 9 1 55.8 4 1.5 1.6 58 13 0.5 9 2 56.1 2.558 13 0.5 9 3 56.0 3.5 1 1.4 40 9 0.5 9 1 55.5 8.2 5.6 3.2 40 9 0.5 9 255.8 2.6 40 9 0.5 9 3 56.0 4.9 2.3 1.9

These experiments demonstrate that when using a short bus with the lowsheet resistance electrode it is beneficial to increase the bus lengthto the opposite electrode to improve uniformity. Ideally, therefore forlarge mirrors we prefer the ratio of the lengths of the bus bars to begreater than 5:1, preferably greater than 9:1, even more preferablygreater than 13:1 and most preferably greater than 20:1 to attain atiming factor below 3. We also find that independent of the length ofthe smaller bus that uniformity improves by increasing the length of thebus to the higher sheet resistance electrode to acquire a contactpercentage preferably greater than approximately 58% and more preferablygreater than approximately 85%. Typical large EC mirrors have a contactpercentage less than 50%.

These findings are critical not only to mirrors with opaque reflectorsbut they are even more critical to mirrors employing transflectivereflectors. In order to have a transflective coating the metals must bethinned to the point of transparency. The thinner metals therefore havehigher sheet resistance values. In at least one embodiment of thepresent invention an electro-optic element comprises fast, uniformdarkening with traditional bus bar arrangements with the optional pointcontact bus arrangements taught herein. Novel transflective coatings aredescribed below that are particularly well suited to complement the busarrangements described above.

One may also pattern the conductivity underneath an opaque cover layeror stack of layers that are opaque, in order to enable an electrochromicmirror to darken more uniformly over its entire area or to darken fromits center first (where most headlight glare appears) outward toward thetop and bottom of the viewing area. U.S. Patent Application20040032638A1 “Electrochromic devices with thin bezel-covered edge”Tonar, et. al. hereby incorporated by reference, mentions that “lowersheet resistance coating may be provided in an area proximate theassociated electrical contact or around a perimeter area and allow thesheet resistance to increase as the distance from the electrical contactincreases” and states that “this is particularly applicable when pointcontacts are utilized”. One would typically want to provide contrast inohms without any, or very minimal, visible contrast in the reflectorwhen the electrochromic element has no voltage applied to it.

In order to obtain sufficient contrast between the more and less highlyconductive areas of an electrochromic device to enable preferentialdarkening of certain areas, it may be necessary to include in the stackmaterials that are not metallic. This is because opaque layers or stacksof the more reflective metals and alloys tend to be conductive enough toprovide acceptable darkening characteristics in an automotiveelectrochromic mirror without the supplement of more highly conductivepatterns underneath them. One example of such a materials stackincluding semi-metals is one constructed similarly to those described inU.S. Pat. No. 5,535,056, “method for making elemental semiconductormirror for vehicles” hereby incorporated by reference, where an opaquesilicon layer would be covered by approximately one quarter wave opticalthickness of Indium Tin Oxide covered by 20 to 25 nanometers of Silicon,covered by approximately 20 nm of Indium Tin Oxide. Such a coatingstack, being opaque could have additional materials placed beneath it inpatterns with minimal effect on its appearance from the front. Thisstack would also be sufficiently conductive throughout to not lose theadvantages of that patterning. In addition, the ITO, if found to stillbe too conductive when deposited under conditions that usually yieldapproximately 12 ohms per square at about 1400 Angstroms thickness, canbe made less conductive by adjusting process conditions or by changingthe indium to tin ratio.

Elements constructed in accordance with the principles described inUS20040032638A1 with the geometry of FIGS. 5 f and 7, having conductiveepoxy along top, lower and left edge, and point contact made atapproximately the middle of the right edge were made with differentthird surface coating stacks and conductivity patterns. When mention ofthe entire third surface is made that will refer to the surface prior toany lasering to create the insulating areas necessary for theconstructions in accordance with commonly assigned U.S. PatentApplication 20040022638A1.

Elements with ½ ohm per square third surface reflectors over theentirety of the viewing area were contrasted with those that had ½ ohmper square in a stripe of ½″ or 1″ or 2″ across the center of theelement covered by an opaque layer such that there was 4 Ohms per squareconductivity in the remainder of the viewing area and yet fairly uniformappearance of the elements in the bright state. Upon darkening theelements there was a slight decrease in the tendency for the center ofthe element to lag in darkening when compared to the edges with thecontrasting regions of conductivity.

In order to have a higher level of conductivity contrast, elements weremade similar in construction to those in the preceding paragraph but onthe third surface ITO of approximately 12 ohms and 40 ohms per square,respectively, had a conductive stripe of silver of 2″ placed across thecenter of the single which (for processing durability) then was coveredwith a flash layer of transparent conductive oxide. After being madeinto full electrochromic devices, the elements were placed over asilvered piece of glass so that in evaluating the darkeningcharacteristics there would be a reflector of similar strength to thesilver stripe behind the regions with 12 ohm/sq. and 40 ohm/sq. ITO,which are relatively transparent. It was seen that the device with 40Ohm/sq. to ½ ohm/sq. contrasting regions on the third surface had lessof an iris effect when darkening than the element with 12 ohm/sq to ½ohm/sq contrasting regions when viewed under these conditions.

Elements were made per the preceding paragraph except that additionalcoatings were used on the third surface. Those coatings consisted of: anadditional flash layer of conductive oxide (put there for adhesion sincethe processing involved vacuum breaks in the coating process),approximately 300 nm Silicon, approximately 60 nm ITO, another 20 nmSilicon and then 10 nm ITO. The silicon layer may be prone to surfaceoxidation which may in certain EC elements may form a surface oxide thatthen interferes with the uniformity and consistency of darkening. TheITO or other TCO or another material described herein as a flash layeror overlayer may be used to inhibit the formation or negative effects ofsaid oxide. Those elements which had started with the initial layer (perthe preceding example) of 40 ohms per square had resulting third surfaceconductivities that were about 24 ohms/square in the top and bottomregions (per FIGS. 5 f and 7), and <1 ohm/square in the center region asmeasured by four point probe. The elements which had started with aninitial ITO layer of 12 Ohms/square had 10-12 ohms per square in the topand bottom regions. As per the previous example the elements with higherohmic contrast had the least iris effect or the most tendency to centerto edge darken. These elements also had the following opticalcharacteristics in the unpowered state when using D65 2 degree observer,

L* a* b* Y Higher ohmic contrast (50 ohm base layer) 76 −5 4 50 Lowerohmic contrast (12 ohm base layer) 75 −3 5 51

Preferential darkening of certain areas of the electrochromic device mayalso be obtained by means of thin deletion lines in the second surfacetransparent conductor (stack) or third surface reflective (stack), aswell as grading the thickness of the coatings as described elsewhereherein. Using laser deletion as an example, in general, as one decreasesthe operating wavelength of a laser it is capable of creating a thinnerlaser line. 15 micron width deletion lines, have been produced using UVlaser of wavelength 355 nm. These lines are still discernable but muchless so than those produced by using longer wavelength lasers. Asshorter wavelength lasers continue to become more accessible one mayfairly anticipate that deletion lines that are not cosmeticallyobjectionable in the viewing area under normal conditions for anautomotive mirror will be possible.

When at the lines or portions of the lines indicated across the centerof FIGS. 5 f and 7 there are deletions of the coating stack that willbecome the third surface of the element, and then elements areconstructed in accordance with prior techniques so that there is arelatively small contact at one edge of the part and conductive epoxyused on the other three sides of the element the darkeningcharacteristics are affected.

Patterns of deletion, by laser, were made for both the lines showninterior to the element as described in FIGS. 5 f and 7 on a ½ ohm persquare reflector electrode as follows:

-   1) There was complete deletion of coating in a thin line extending    form the edge of the glass to 15 cm from the edge of the glass.-   2) There was complete deletion of coating in thin lines in a    repeating pattern of 8 mm deletion and 2 mm unablated across the    entire width of the part.-   3) There was complete deletion of coating in a thin line extending    from the edge of the glass to 14 cm from the edge and then deletion    in a repeating pattern of 5 mm no oblation and 5 mm deletion across    the remainder of the part.-   4) There was complete deletion of coating in a thin line extending    from the edge of the glass to 15 cm from the edge with the exception    of 2 unablated segments of 0.4 mm at approximately 5 and 10 cm along    the line.

When compared to similar parts without any deletion lines these elementsexhibited some to substantially less “iris effect” when darkening.Pattern 4 being the best for overall cosmetics and even darkening amongthose with deletion patterns. Nonetheless all of these patterns wouldneed adjustment for acceptable darkening cosmetics but movement towardsa desired darkening characteristic has been shown.

With reference to FIG. 8 a, a profile view of a portion of a rearviewmirror element is depicted comprising a first substrate 802 a having atleast one layer 808 a of a substantially transparent conductive materialdeposited on the second surface and a second substrate 812 a having astack of materials deposited on the third surface secured in a spacedapart relationship with respect to one another via a primary sealmaterial 878 a to define a chamber there between. In at least oneembodiment, an electro-optic medium 810 a is located within saidchamber. In at least one embodiment, the third surface stack ofmaterials comprises an underlayer 818 a, a conductive electrode layer820 a, a metallic layer 822 a and a conductive tab portion 882 a havingan overlap portion 883 a underneath the metallic layer and primary sealmaterial. It should be noted that the conductive tab portion 882 a couldalternatively be deposited over the metallic coating 822 a to create theoverlap portion. In at least one embodiment, the underlayer istitanium-dioxide. In at least one embodiment, the underlayer is notused. In at least one embodiment, the conductive electrode layer isindium-tin-oxide. In at least one embodiment, the conductive electrodelayer is omitted. In at least one embodiment, the conductive electrodelayer is omitted and the underlayer is either a thicker layer oftitanium-dioxide or some other substantially transparent material havinga relatively high index of refraction (i.e. higher index of refractionthan ITO), such as, silicon carbide. In at least one embodiment, theconductive tab portion comprises chrome. It should be understood thatthe conductive tab portion may comprise any conductive material thatadheres well to glass and/or other stack layers or the epoxy dependingon the layers sequence and is resistant to corrosion under vehicularmirror testing conditions. As can be appreciated, when the third surfacestack of materials, or at least those layers within the stack that aresusceptible to corrosion, are kept within an area defined by an outeredge of the primary seal material, the element will be substantiallyimmune to problems associated with third surface corrosion. It should beunderstood that the layer, or layers, susceptible to corrosion mayextend beyond the primary seal material provided a protective overcoator sealant is incorporated, such as, conductive epoxy or an overcoatlayer. It should be understood that any of the first, second, third andfourth surface layers or stacks of materials may be as disclosed hereinor within the references incorporated elsewhere herein by reference. Itshould be understood that the conductive tab portion improvesconductivity over the conductive electrode; as long as a conductiveelectrode layer is provided with sufficient conductivity, the conductivetab portion is optional. In at least one embodiment, the conductiveelectrode layer imparts the desired color specific characteristics ofthe corresponding reflected light rays in addition to providing thedesired conductivity. Therefore, when the conductive electrode isomitted color characteristics are controlled via the underlayer materialspecifications.

Turning to FIG. 8 b, a profile view of a portion of a rearview mirrorelement is depicted comprising a first substrate 802 b having at leastone layer 808 b of a substantially transparent conductive materialdeposited on the second surface and a second substrate 812 b having astack of materials deposited on the third surface secured in a spacedapart relationship with respect to one another via a primary sealmaterial 878 b to define a chamber there between. In at least oneembodiment, an electro-optic medium 810 b is located within saidchamber. In at least one embodiment, the third surface stack ofmaterials comprises an underlayer 818 b, a conductive electrode layer820 b, a metallic layer 822 b and a conductive tab portion underneaththe primary seal material. In at least one embodiment, a void area 883 cis defined between the metallic layer and the conductive tab portion,the conductive electrode provides electrical continuity there between.In at least one embodiment, the underlayer is titanium-dioxide. In atleast one embodiment, the underlayer is not used. In at least oneembodiment, the conductive electrode layer is indium-tin-oxide. In atleast one embodiment, the conductive tab portion comprises chrome. Itshould be understood that the conductive tab portion may comprise anyconductive material that adheres well to glass and/or other stack layersor the epoxy depending on the layers sequence and is resistant tocorrosion under vehicular mirror testing conditions. As can beappreciated, when the third surface stack of materials, or at leastthose layers within the stack that are susceptible to corrosion, arekept within an area defined by an outer edge of the primary sealmaterial, the element will be substantially immune to problemsassociated with third surface corrosion. It should be understood thatany of the first, second, third and fourth surface layers or stacks ofmaterials may be as disclosed herein or within the referencesincorporated elsewhere herein by reference.

With reference to FIG. 8 c, a profile view of a portion of a rearviewmirror element is depicted comprising a first substrate 802 c having atleast one layer 808 c of a substantially transparent conductive materialdeposited on the second surface and a second substrate 812 c having astack of materials deposited on the third surface secured in a spacedapart relationship with respect to one another via a primary sealmaterial 878 c to define a chamber there between. In at least oneembodiment, an electro-optic medium 810 c is located within saidchamber. In at least one embodiment, a first metallic layer 818 c isdeposited over substantially the entire third surface. In at least oneembodiment, a second metallic layer 820 c is deposited over the firstmetallic layer such that an outer edge of the second metallic layer islocated within an area defined by an outer edge of a primary sealmaterial 878 c. In at least one embodiment, the first metallic layercomprises chrome. In at least one embodiment, the second metallic layercomprises silver or a silver alloy. It should be understood that any ofthe first, second, third and fourth surface layers or stacks ofmaterials may be as disclosed herein or within the referencesincorporated elsewhere herein by reference.

Turning to FIG. 8 d, a second substrate 812 d is depicted comprising astack of materials having an eyehole 822 d 1 substantially in front of alight sensor or information display. In at least one embodiment, a firstmetallic layer 818 d is provided with a void area in the eyehole area.In at least one embodiment, a second metallic layer 820 d is providedwith a void area in the eyehole area. In at least one embodiment, athird metallic layer 822 d is provided. In at least one embodiment, onlythe third metallic layer is deposited in the eyehole area. In at leastone embodiment, the first metallic layer comprises chrome. In at leastone embodiment, the second metallic layer comprises silver or silveralloy. In at least one embodiment, the third metallic layer comprises athin silver, chrome or silver alloy. It should be understood that any ofthe first, second, third and fourth surface layers or stacks ofmaterials may be as disclosed herein or within the referencesincorporated elsewhere herein by reference.

Turning to FIGS. 9 a-k there are shown various options for selectivelycontacting a particular portion of the second and third surfaceconductive electrode portions 922, 908. As can be appreciated, theconfiguration of FIG. 7 results in the electrically conductive materialcontacting at least a portion of each the second and third surfaceconductive electrode portions. It should be understood that the contactconfigurations as shown may be rotated about the element in any fashion.

The element construction depicted in FIG. 9 a comprises a firstsubstrate 902 a having a second surface stack of materials 908 a and asecond substrate 912 a having a third surface stack of materials 922 a.The third surface stack of materials is shown to have an isolation area983 a such that a portion of the third surface stack of materials thatis in contact with a conductive epoxy 948 a is isolated from theremainder of the third surface stack of materials. The first and secondsubstrates are held in spaced apart relationship to one another via aprimary seal material 978 a. It should be understood that another sideof the element may have a similar isolation area associated with thesecond surface stack of materials for providing contact to the thirdsurface stack of materials within the viewing area. It should beunderstood that either the second or third surface stack of materialsmay be a single layer of materials as described elsewhere herein andwithin references incorporated herein by reference.

The element construction depicted in FIG. 9 b comprises a firstsubstrate 902 b having a second surface stack of materials 908 b and asecond substrate 912 b having a third surface stack of materials 922 b.The first and second substrates are held in a spaced apart relationshipwith respect to one another via a primary seal material 978 b. Anelectrically conductive epoxy 948 b is in contact with the third surfacestack of materials and electrically insulated from the second surfacestack of materials via the insulating material 983 b. It should beunderstood that another side of the element may have a similar isolationarea associated with the second surface stack of materials for providingcontact to the third surface stack of materials within the viewing area.It should be understood that either the second or third surface stack ofmaterials may be a single layer of on materials as described elsewhereherein and within references incorporated herein by reference.

The element of FIG. 9 c comprises a first substrate 902 c having asecond surface stack of materials 908 c and a second substrate 912 chaving a third surface stack of materials 922 c. The first and secondsubstrates are held in spaced apart relationship with respect to oneanother via a primary seal material 978 c. The second surface stack ofmaterials extends toward the edge of the first substrate beyond theprimary seal material such that it is in electrical contact with a firstelectrically conductive epoxy, or first solder, 948 c 1. The thirdsurface stack of materials extends toward the edge of the secondsubstrate beyond the primary seal material such that it is in electricalcontact with a second electrically conductive epoxy, or second solder,948 c 2. It should be understood that another side of the element mayhave a similar isolation area associated with the second surface stackof materials for providing contact to the third surface stack ofmaterials within the viewing area. It should be understood that eitherthe second or third surface stack of materials may be a single layer ofon materials as described elsewhere herein and within referencesincorporated herein by reference.

FIG. 9 d depicts the second surface electrical contact 948 d 1 beingmade on an opposite side of the element from a third surface electricalcontact 948 d 2. FIG. 9 e depicts the second surface electrical contact948 e 1 being made on a side of the element and the third surfaceelectrical contact being made on an end of the element. FIG. 9 f depictsthe second surface electrical contact 948 f 1 being made on one side andcontinuously with one end of the element and the third surfaceelectrical contact 948 f 2 being made on an opposite side andcontinuously with an opposite end of the element. FIG. 9 g depicts thesecond surface electrical contact 948 g 1 being made on opposite sidesof the element and the third surface electrical contact 948 g 2 beingmade on an end of the element. FIG. 9 h depicts the second surfaceelectrical contact 948 h 1 being made on opposite sides of the elementand the third surface electrical contact 948 h 2 being made on oppositeends of the element. FIG. 9 i depicts the second surface electricalcontact 948 i 1 being made continuously on opposite ends and one side ofthe element and the third surface electrical contact 948 i 2 being madeon one side of the element. FIG. 9 j depicts the second surfaceelectrical contact 948 j 1 being made continuously on opposite ends,completely on one side and on at least one portion on the second sideand the third surface electrical contact 948 j 2 being made on one sideof the element. It should be understood that, in at least oneembodiment, the longer electrical contact will correspond to the surfacehaving the highest sheet resistance stack of materials. It should beunderstood that the electrical contact may be via electrical conductiveepoxy, solder or an electrically conductive adhesive.

FIG. 9 k depicts an element comprising a first substrate 902 k having asecond surface stack of materials 908 k and a second substrate 912 khaving a third surface stack of materials 922 k. The first and secondsubstrates are held in spaced apart relationship with respect to oneanother via perimeter first and second primary seals 948 k 1, 948 k 2.The first primary seal functions to make electrical contact with thesecond surface stack of materials and the second primary seal functionsto make electrical contact with the third surface stack of materials.The first and second primary seals hold the first and second substratesin a spaced apart relationship with respect to one another andpreferably both primary seals are substantially outside the edge of eachsubstrate.

Another approach for establishing an electrical connection to anelectrode or contact clip, such as a J clip or L clip, of anelectro-optic element is through a solid phase welding process. Wirebonding is a welding process that is used in the electronics industry toestablish reliable interconnections between electronic components(usually IC chips and chip carriers). A wire bonding process isdescribed in Chapter A by Zonghe Lai and Johan Liu in Nordic ElectronicsPackaging Guidelines. Electrical interconnections made by wire bondingemploy a metal wire or ribbon and a combination of heat, pressure and/orultrasonic energy to weld the wire or ribbon to an associated metalsurface. Typically the wire or ribbon is welded using a special wedge orcapillary bonding tool. Typical bonding processes use heat and orultrasonic energy and generally fall into three major categories:thermocompression bonding, ultrasonic bonding and thermosonic bonding. Awire being bonded may be terminated at the bond or multiple bonds may bemade with a continuous wire. Common forms of wire bonds include a ballbond, wedge bond and stitch bond. Wires and ribbons made of manydifferent metals and alloys may be wire bonded including aluminum, gold,silver, copper and alloys thereof. These wires may be bonded to a numberof metals or substrates coated with metal layers including but notlimited to metal layers of gold, silver, nickel, aluminum and alloysmade with these metals. In the case of bonding to electrodes ofelectro-optic elements the preferred substrate is glass and thepreferred metal deposition process is by a physical vapor depositionprocess such as magnetron sputtering. A glue layer or layers such as ofchrome, molybdenum, nichrome or nickel may be applied between the wirebonded metal layer and glass to obtain acceptable adhesion. Thedeposited metal layer thickness may be between 5 Angstroms to 1000microns. More preferably the metal layer thickness is between 100Angstroms and 1 micron and most preferably the metal layer thickness isbetween 200 and 1000 Angstroms. The wire diameter or ribbon thicknessmay be between 10 and 250 microns with diameters or thicknesses between25 and 100 micron being preferred and diameters or thickness between 50and 75 microns being most preferred. In at least one embodiment Acontinuous wire may be wedge or stitch bonded along a perimeter edge ofa substrate such as to a chrome ring on a second surface of anelectrochromic mirror. A wire or ribbon bus may be electricallyconnected to a clip such as a nickel J or L clip by welding the wire orribbon to the clip and then looping the cup to the substrate and weldingit to the associated electrode. The wire or ribbon may start at themetal clip and progress along the EC electrode or start along the ECelectrode and loop to the clip and back to the electrode. In at leastone embodiment, it is preferred to have redundant welded connections tothe associated electrode and/or from the EC electrode to the associatedelectrical contact clip for reliability and uniform coloration of thedevice. Multiple welded connections to the substrate may be made atspacings from every 0.005 inches to 10 inches with spacings of 0.040inches to 2 inches being preferred and with spacings between 0.100 and0.50 inches being most preferred. A welded wire or ribbon bus may beprotected from damage by encapsulating the wire and welds in a sealant.A preferred method is to protect the bus by encapsulating thewire/ribbon and welded bonds in the perimeter seal of the associatedelement. The metal wire/foil is chemically compatible with the EC mediaenclosing the bus in the device (inside the perimeter seal) ispreferred. A wire bus may also be used to supplement the conductivity ofthe associated electrode inside the element. Wires with diameters of 75microns or less are not readily apparent to the human eye. Welded wirebonding is attractive from a manufacturing perspective because it is aroom temperature or low temperature process, there is no post cure orpost processing operations required, the technology is well establishedwith proven reliability and the bonds may be quickly (around 100millisecond per bond) established.

Wire bonding may also be used to electrically connect electroniccomponents to the substrate surfaces of an element. For example, manymetals are electrochemically stable when used as a cathode but not as ananode in an element. It is desirable to provide protection such as by adiode to limit operation of the EC device when the polarity is reversed.(This is described in detail below with reference to FIG. 11 a-c.) Anelectrical component such as a surface mount diode may be attached tothe substrate or the bus clip and electrically connected to thesubstrate and/or the clip by wire bonding. In another embodiment, lightemitting diodes (LED's) that are part of a signaling or warning systemmay be attached, for example in chip form, to an associated substrateand electrically connected to a circuit on the substrate formed bypatterning metal coatings by etching, masking or laser ablation. TheseLED's or other electrical components may be mounted on or in the elementon substrate surfaces one, two, three or four. Often it is desirable toincrease the drive voltage applied to a solution phase electrochromicdevice as the temperature increases to compensate for the increasedrates of diffusion of the electrochromic species and maintain gooddevice darkening properties over a wide temperature range. A thermistorand electronic components required for a temperature modulated variablevoltage drive circuit may be mounted to an associated substrate surfaceand electrically connected to metal coatings on the substrate by wirebonding Example: Aluminum wires bonded to metal coatings on a glasssubstrate as follows:

Glass washed and vacuum sputter coated with approximately 400 Angstromthick layers comprising a first layer of chrome and second layer ofnickel (CN); a first layer of chrome and second layer of ruthenium (CR);a first layer of chrome, a second layer of ruthenium and third layer ofnickel (CRN). A 0.00125″ diameter aluminum alloy wire containing 1%silicon (1-4% elongation, 19 to 21 grams tensile strength) wire bondedto the metal coated glass substrates using a Westbond Model 454647Ewirebonder with the following settings:

Settings First Bond Second Bond

“CN” Power 175 150

Time 30 millisecond 30 millisecond

Force 26 grams 26 grams

“CRN” Power 175 150

Time 30 milliseconds 30 milliseconds

Force 26 grams 26 grams

“CR” Power 150 125

Time 75 milliseconds 100 milliseconds

Force 26 grams 26 grams

Bond strength of the wire was evaluated by pulling off the wire afterbonding and after 1 hour exposure to 300 degrees centigrade andmeasuring the force.

Wire Bond Mean Pull Strength:

After Bonding After 300 C bake

“CN” 14.51 grams 9.02 grams

“CRN” 19.13 grams 8.2 grams

“CR” 12.42 grams 8.7 grams

Predominate failure after bonding was wire break at the end of firstwelded bond. After bake the predominate failure was wire break at midspan for “CN” and “CRN” groups and wire break at the end of first bondfor the “CR” group. This example demonstrates multiple reliable weldedbonds may be made to typical sputtered metal layers on glass.

FIG. 10 generally illustrates variable transmittance windows 1010 thatmay be employed in multi-passenger vehicles, along with a window controlsystem 1008 electrically coupled to the variable transmittance windows1010 for controlling the transmittance state of the variabletransmittance windows 1010. Window control system 1008 includes a windowcontrol unit 1009 coupled to each of the variable transmittance windows1010 for controlling the transmittance of 7 each of the variabletransmittance windows 1010. Each window control unit 1009 includes slavecontrol circuitry 1070 for controlling the transmittance state of anassociated variable transmittance window 1010. Each window control unit1009 is also shown having user input mechanism 1060 coupled to slavecontrol circuitry 1070 for providing a user input to slave controlcircuitry 1070 to change the transmittance state of the associatedvariable transmittance window 1010. Each window control unit 1009 isalso shown coupled to power and ground lines 1011 for providing power toslave control circuitry 1070, user input mechanism 1060, and variabletransmittance window 1010. As shown, power is provided to variabletransmittance window 1010 via slave control circuitry 1070 from thepower and ground lines 1011.

Each window control unit 1009 is also shown coupled to a window controlsystem bus 1013. Other devices also coupled to the window control systembus 1013 include master control circuitry 1090 and other electronicdevices 1092. Master control circuitry 1090 is configured to monitorsignals provided on the window control system bus 1013 by each of windowcontrol units 1009 and to provide control signals on the bus to each ofwindow control units 1009. Master control circuitry 1090 includesprocessing circuitry, including logic, memory, and bus interfacecircuitry, to permit master control circuitry 1090 to generate, send,receive, and decode signals on the window control system bus 1013. Slavecontrol circuitry 1070, included in each of window control units 1009,is configured to receive a desired window transmittance state from userinput mechanism 1060, and provide electrical signals to variabletransmittance window 1010 to change the transmittance state of variabletransmittance window 1010 to the state requested by the user via userinput mechanism 1060. Slave control circuitry 1070 is also configured tomonitor various characteristics of variable transmittance window 1010,including the power consumed by variable transmittance window 1010 andthe transmittance state of variable transmittance window 1010. Slavecontrol circuitry 1070 also includes circuitry for receiving signalsfrom, and sending signals to, the window control system bus 1013.

Certain metal films can be less stable when configured as an anode whencompared to transparent conductive oxides, such as, indium tin oxidefilms. This may be evidenced upon cycling in an electrochromic device bythe metal deplating from the anode or by chemical changes in the metalsurface such as oxidation, or by the surface becoming hazy from themobile metal atoms rearranging into a rougher surface. Some metals andmetal thin film stacks and thin film stacks containing metallic layerswill be more resistant to these effects than others. Nonetheless it maybe desirable to take steps to insure that the third surface reflectorelectrode is the cathode.

It is possible that in certain embodiments it might be preferable toincorporate materials into the second surface transparent electrode thatare sensitive to use as an anode. In this case it may be preferable todrive the third surface electrode as the anode and the second surfaceelectrode as the cathode in order to protect the second surfaceelectrode.

For electrochromic mirrors on the exterior of a vehicle there may be apower source that is not directly tied to an associated drive circuitlocated in an associated interior mirror which may to some degreeminimize the risk of the third surface reflector electrode being theanode on that mirror (i.e. the given exterior mirror may comprise anindependent drive circuit). However, it is common for the power of anexterior mirror (or mirrors) to be supplied via the interior mirror.There are oftentimes several connections between an interior mirror andcorresponding exterior mirror(s). The risk of the polarity of the powerfrom the interior mirror to the exterior mirror being reversed, makingthe third surface reflector electrode of the device and anode, may beunacceptable when the associated reflector/electrode is not sufficientlydurable to function as an anode.

With reference to FIG. 11 a, a circuit 1101 a having a diode in serieswith an exterior mirror element 1102 a, prevents current flow withreversed polarity, as well as preventing electrochromic functionality.The device may have compromised performance when operated in the correctpolarity in that the mirror will darken upon application of the usualvoltage however upon shorting of the circuit at the inside mirrorcircuitry for clearing, the exterior mirror will not be able todischarge via that route. Therefore the exterior mirror element willmainly discharge as the positive and negatively charged speciesneutralize each other in solution, however not as they discharge to theconductive surfaces of the device. This may result in a substantiallyslowed clearing speed for the device.

The circuit 1100 b depicted in FIG. 11 b comprises a diode 1101 b inparallel across the leads near an exterior mirror element 1102 b. Ashort circuit will be caused if the polarity of the current provided tothat portion of circuit is reversed. Current will then flow through thediode and not the electrochromic element. The short is detected by theinterior mirror circuitry 1103 b and voltage is automaticallydisconnected. Therefore, even though allowing proper operation of themirror when the polarity is correct, this circuit completely disablesthe electrochromic functionality of the mirror if the polarity isreversed.

However, when a diode 1101 c is coupled with circuitry 1100 c that doesnot initially cease to apply voltage when excessive current (shorting)however reverses voltage the mirror element 1102 c remains operationaland the proper polarity is delivered to the element such that thereflector electrode automatically is reconnected as the cathode. In thiscircuit 1100 c when excessive current is detected two solid stateswitches 1104 c 1, 1104 c 2 are automatically reconfigured to redirectthe current through the element 1102 c in the opposite direction. Shouldexcessive current be detected in this configuration, the solid stateswitches are reset and the drive to the element is discontinued since itis likely that some other fault is causing the excessive current draw.

FIG. 11 d depicts an alternate configuration for an electro-optic drivecircuit that provides automatic compensation for reverse polarity.Diodes 1101 d 1, 1101 d 2, 1101 d 3, 1101 d 4 define a rectifier bridgewhich provides a dual current path. The actual path current flows willalways have the desired orientation of anode and cathode of theelectro-optic element 1102 d.

The circuits 1100 a, 1100 b, 1100 c, 1100 d of FIGS. 11 a-11 d aredepicted to a single outside mirror. Should it be desirable to protectmore than a single exterior mirror the desired circuitry may be soadapted.

In electro-optic elements similar to that shown in FIG. 7, having afourth surface reflector (not shown), when there is no electricalpotential difference between transparent conductors 708 and 718, theelectrochromic medium in chamber 710 is essentially colorless or nearlycolorless, and incoming light (I_(o)) enters through the front element702, passes through the transparent coating 708, the electrochromicmedium in chamber 710, the transparent coating 718, the rear element712, and reflects off the layer and travels back through the device andout the front element 702. It should be understood that aspects of thepresent invention directed toward variable transmittance windows asdescribed above may not incorporate a reflective layer. In otherembodiments a third surface reflector/electrode may be employed.Typically, the magnitude of the reflected image (I_(R)) with noelectrical potential difference is about 45 percent to about 85 percentof the incident light intensity (I_(o)). The exact value depends on manyvariables outlined below, such as, for example, the residual reflection(I′_(R)) from the front face of the front element, as well as secondaryreflections from the interfaces between the front element 702 and thefront transparent electrode 708, the front transparent electrode 708 andthe electrochromic medium, the electrochromic medium and the secondtransparent electrode 718, and the second transparent electrode 718 andthe rear element 712. These reflections are well known in the art andare due to the difference in refractive indices between one material andanother as the light crosses the interface between the two. When thefront element and the back element are not parallel, the residualreflectance (I′_(R)) or other secondary reflections will not superimposewith the reflected image (I_(R)) from mirror surface, and a double imagewill appear (where an observer would see what appears to be double, ortriple, the number of objects actually present in the reflected image).

There are minimum requirements for the magnitude of the intensity of thereflected light depending on whether the electrochromic mirrors areplaced on the inside or the outside of the vehicle. For example,according to current requirements from most automobile manufacturers,inside mirrors preferably have a minimum high end reflectivity of atleast 40 percent, and outside mirrors must have a minimum high endreflectivity of at least 35 percent.

The electrode layers 708 and 718 are connected to electronic circuitry,FIGS. 10-11 d for example, which is effective to electrically energizethe electrochromic medium, such that when a potential is applied acrossthe conductors 708 and 718, the electrochromic medium in chamber 710darkens, such that incident light (I_(o)) is attenuated as the lightpasses toward the reflector and as it passes back through after beingreflected. By adjusting the potential difference between the transparentelectrodes, a preferred device functions as a “gray-scale” device, withcontinuously variable transmittance over a wide range. Forsolution-phase electrochromic systems, when the potential between theelectrodes is removed or returned to zero, the device spontaneouslyreturns to the same, zero-potential, equilibrium color and transmittanceas the device had before the potential was applied. Other materials areavailable for making electrochromic devices and it should be understoodthat aspects of the present invention are applicable irrespectively ofwhich electro-optic technology is employed. For example, theelectro-optic medium may include materials that are solid metal oxides,redox active polymers, and hybrid combinations of solution-phase andsolid metal oxides or redox active polymers; however, theabove-described solution-phase design is typical of most of theelectrochromic devices presently in use.

Various attempts have been made to provide an electro-optic element witha second surface transparent conducting oxide with a relatively lowsheet resistance while maintaining low absorption. In the electrochromicmirrors described above as well as in electrochromic windows orelectro-optic devices in general, the transparent conductive layers 708,718 are often made of indium tin oxide. Other attempts have focused onreducing the intrinsic stress of an ITO layer as applied to anassociated glass substrate to minimize bending or warping of thesubstrate. Still other attempts have been made to optimize the opticalproperties such as the reflectance by adjusting the quarter and, or,half wave thickness of the ITO layer(s), or to minimize the weight ofthe overall associated assembly. However, there has been little successin efforts to simultaneously optimize all of the optical and physicalproperties noted above due to the previously perceived physicallimitations.

One such previous approach to optimizing the optical properties of agiven electrochromic assembly has been to manipulate the composition ofthe electrodes therein. Specifically, certain optical properties may beobtained by adjusting the reflectance of the reflective electrode of theassembly. More specifically, by manipulating the material composition ofthe stacked layers comprising the reflective electrode, the reflectivitythereof may be increased, thereby nullifying the relative absorption ofthe associated transparent electrode. However, increasing thereflectivity of the reflective electrode typically requires the use ofadditional amounts of the metals used to construct the same, such asrhodium, ruthenium, chrome, silver, and the like. As many of thesemetals are relatively expensive, adding additional amounts thereof tothe electrochromic element unacceptably raises the cost thereof.Moreover, many lower cost metals, while providing good reflectiveproperties, are incompatible with manufacturing processes and/or withthe harsh environmental conditions to which the overall assembly will besubjected, such as, exterior mirror assemblies and exterior windowassemblies.

Other approaches, which utilize ITO electrodes, required the balancingof several optical and physical parameters that are non-complimentary toone another. For example, increasing the thickness of a transparent ITOconductive layer to achieve a lower sheet resistance may adverselyeffect the absorption associated with that layer, the position of thequarter and, or, half wave points, and the bending of the substrate towhich the ITO layer is applied, as is discussed in detail below.

As known in the art, reducing the sheet resistance of an ITO layer maybe accomplished by increasing the thickness of that layer. However, theincreased thickness of the ITO layer is accomplished with an undesirableincrease in light absorption of that layer. Further, an increase in thethickness of the ITO layer has typically been restricted to quanta ofhalf waves of a given wavelength range (typically centered atapproximately 550 nm) so as to minimize the relative reflectance fromthe outer surface of the ITO layer. Moreover, increasing the thicknessof the ITO layer may increase the bending of the substrate to which theITO layer is applied. As is known, the ITO layer includes an internalstress that is exerted on the substrate, which when applied to some thinsubstrates, may result in bending of such substrate. In manyapplications, the substrate comprises relatively thin glass, so as toreduce absorption of the glass and the weight associated therewith, suchthat unacceptable bending occurs as the thickness of the ITO layer isincreased. This is particularly prevalent in large applications, such aslarge windows such as those used within aircraft or in buildings.Bending of the associated substrate may effect the distance between thetwo electrodes within the overall assembly, thereby effecting clearingrates, color, relative uniformity darkness or brightness of the assemblyat varying points across the surface thereof, and even causing opticaldistortions to the point of created multiple reflected images ratherthan a single image. Previous approaches at reducing the intrinsicstress of the ITO layer have focused on the methods utilized to producethe electrochromic elements. One method known in the art for applyingthe ITO layer to an associated substrate includes magnetic sputtering.Heretofore, these attempts have only been moderately successful due toseveral drawbacks, one of which is the physical limitations inherent inthe approach, an example of which is the disruption of the laydown ofthe ITO layer at increased pressure, resulting in clustering of the ITO.Such clustered ITO layers exhibit an increase in sheet resistance, hazeand absorption.

In at least one embodiment an electro-optic element is providedutilizing an ITO layer having reduced sheet resistance, reducedabsorption, and low stress, while attaining a uniform darkness orbrightness of the overall assembly, while reducing the weight of theoverall assembly, any sub combination or combination thereof.

In at least one embodiment an electro-optic element is provided having arelatively reduced sheet resistance while simultaneously providing arelatively reduced absorption, a relatively decreased bending of anassociated substrate to which the associate ITO layer is applied, andprovides a relatively uniform darkness or brightness for the overallassembly while reducing the total weight thereof.

While mirror assemblies in general are utilized herein to describe manydetails of the present invention, it should be noted that embodiments ofthe present invention is equally applicable to the construction ofelectro-optic windows, as discussed elsewhere herein. The inside mirrorassembly of FIGS. 6 a-d and the outside rearview mirror assemblies ofFIGS. 5 a-5 f may incorporate light-sensing electronic circuitry of thetype illustrated and described in Canadian Patent No. 1,300,945, U.S.Pat. No. 5,204,778, or U.S. Pat. No. 5,451,822, and other circuitscapable of sensing glare and ambient light and supplying a drive voltageto the electrochromic element; the disclosures of which are incorporatedin their entireties herein by reference.

As noted above, high performance electro-optic elements (either mirrorsor windows) require that the electrode and or reflector on the thirdsurface and the transparent conductive electrode 708 provide moderate tohigh conductivity to provide even overall coloration, increased speedsof coloration and clearing, etc. While improvements in mirror elementshave been accomplished by employing a third surface reflector/electrode,improvements with respect to the transparent electrode 708, 718 aredesired. As also previously noted, simply increasing the overallthickness of an ITO transparent electrode 708, 718 while improvingconductivity by decreasing the sheet resistance, has detrimental effectson other optical and physical properties of the electrochromic element.Table 4 depicts the drop in reflectance of an EC element with changingITO thickness for three ITO coatings with different optical constants.The different ITO coatings in this example have different imaginaryrefractive indices. The example element construction consists of 1.7 mmglass, 50 nm Cr, 20 nm Ru, 140 microns of EC fluid, varying ITO and 1.7mm of glass. The thickness of different ITO layers is shown in Table 4.In many side mirror applications the customer specifications requirethat the reflectance is greater than 55%. The thickness is limiteddepending on the properties of the ITO and therefore the viable sheetresistance is also limited. In a typical manufacturing process it is notalways possible to operate a process at the lowest absorption levels.Therefore, the practical upper thickness and lower sheet resistancelimits are constrained by the variation in the manufacturing process.Additionally, it is common that ITO with lower absorption undesirablycorresponds to higher sheet resistance. Thicker, low absorption, ITO mayalso correspond to one with a higher sheet resistance thereby limitingthe benefit of the thicker coating.

TABLE 4 Reflectance (%) ITO ITO ITO ITO Thickness RI = 1.893 RI = 1.868RI = 1.865 (nm) k = 0.0057 k = 0.0079 k = 0.012 100 59.8 59.3 58.2 15058.5 57.7 56.0 200 58.4 57.2 55.1 250 57.5 56.2 53.7 300 56.5 54.9 51.9350 56.1 54.3 50.9 400 55.4 53.4 49.6 450 54.5 52.3 48.2 500 54.0 51.647.1

Another design attribute desirably for EC elements is to have a lowreflectance in the dark state. This results in a high contrast ratio forthe mirror elements. Table 5 depicts the dark state reflectance valuesfor an EC mirror as a function of the ITO thickness. In this example theEC fluid is set to be substantially opaque. If the EC fluid is notcompletely opaque then the reflected light from the mirror coating willadd to the reflectance in Table 5. As depicted, the dark statereflectance reaches a minimum at about 140 to 150 nm or a ½ wave coatingwith a design wavelength of 550 nm. As the thickness deviates from thishalf wave thickness, the dark state reflectance rises and the contrastratio degrades. Therefore, ITO thickness cannot be set to an arbitrarythickness to attain a given sheet resistance value. The ITO thickness isconstrained by both absorption of the coating and the dark statereflectance requirements.

TABLE 5 ITO Thickness Dark State (nm) Reflectance (%) 70 9.4 80 9.2 908.6 100 7.7 110 6.7 120 5.8 130 5.1 140 4.9 150 5 160 5.5 170 6.2 180 7190 7.7 200 8.2 210 8.5

In at least one embodiment, an electro-optic element includes at leastone ITO transparent electrode 128 with reduced bulk resistance, therebyimproving conductivity, without simultaneously sacrificing other relatedoptical and physical properties. Specifically, an electro-optic elementis constructed via a sputtering process at relatively high pressures andrelatively high oxygen flow rates. Heretofore, traditional sputteringprocesses utilized for applying an ITO layer to a substrate have beenlimited to certain maximum pressures. Exceeding these pressures haspreviously resulted in a poor quality layer of ITO, or specifically aclustered, non-uniform deposition exhibiting poor electrical and opticalproperties.

In at least one embodiment, the ITO coatings were produced on avertical, in-line sputtering coater. Cathodes were approximately 72″ inlength and either two or four cathodes were used to produce thecoatings. The cathodes were outfitted with ceramic ITO tiles commonlyused in the industry. The conveyor speed was adjusted as necessary toproduce a targeted thickness of coating. The power applied to thecathodes was 5 kilowatts unless otherwise noted. Each process sectionhas two pair of cathodes in an aligned facing configuration. Oxygen gasflows shown herein are for a process section consisting of four cathodesunless otherwise indicated. When two process sections are operated it isassumed that an equivalent amount of oxygen is fed into both chambersand the total amount of oxygen is double that used for four cathodes inone process chamber. Glass substrates were preheated to approximately300 degrees Celsius. The sputtering gas was adjusted to attain a givenpressure and oxygen was introduced at the prescribed flow rate or as apercentage of the total gas fed to the system. It should be understood,however, that the present invention is not limited by the exact flowrates and percentages described herein as one skilled in the art willknow that different chambers have different pumping configurations, gasinlets and manifolds, cathodes and powers and measure their pressure atdifferent points in the process. Rather, one skilled in the art willappreciate the novelty of the method used to produce the coatings andtheir resultant properties including bulk resistance, stress andmorphology and will be able to readily scale or adapt the teachingsherein to a different sputtering system without undo experimentation.Though the majority of the work described herein was conducted with aglass substrate temperature of 300 C the trends and findings will beadaptable to higher and lower temperatures and will yield improvementsover the standard conditions even if the absolute values describedherein are not attained at the different temperatures.

In at least one embodiment of the present invention, increase in processpressure is offset by an increase in oxygen flow. As describedparticular relation of pressure to oxygen flow rate depends on severalfactors, including the particular noble gas used during the sputteringprocess. Two noble gases, krypton, and argon, are discussed in detailherein, however, other gases may be utilized with the particulars forthe other gases being extrapolated from the given data.

With respect to krypton, a pressure of greater than or equal to 1millitorr (mT) with an oxygen percentage of 5%, is preferred, a pressureof greater than or equal to 2 mT with an oxygen percentage of 4% is morepreferred a pressure of greater than or equal to 3 mT with an oxygenpercentage of 3% is even more preferred, and a pressure of greater thanor equal to 4.5 mT with an oxygen flow rate of 2% is most preferred.

With respect to argon, a pressure of greater than or equal to 2 mT withan oxygen percentage of 4% is preferred, a pressure of greater than orequal to 3 mT with an oxygen percentage of 3% is more preferred, apressure of greater than or equal to 4.5 mT with an oxygen percentage of2% is even more preferred and a pressure of greater than or equal to 6mT with an oxygen percentage of 1% is most preferred.

As noted above, other gases may also be utilized. For example, Neon maybe used with expected higher pressures, preferably greater than or equalto 3 mT and more preferably greater than or equal to 7 or 8 mT. Further,Xenon allows use of relatively low pressures as compared to krypton. Oneskilled in the art will also recognize that the preferred oxygenpercentages may vary with the details of the sputtering apparatus. Thepercentages listed above are meant to be illustrative and non-limiting.The total flow of oxygen needed to obtain the optimal combination ofmaterial properties will generally increase with increased pressure. Theneeded amount of oxygen does not increase at the same rate as thesputtering gas, therefore, the percentage of oxygen decreases withincreased pressure.

Typically, ITO is run at low pressures—at or below 2 mT. Low pressure,however tends to result in the ITO coating having compressive stress.Stress in the ITO can be high enough to bend glass especially as thethickness of the glass is reduced. As the thickness of the glass isreduced to make EC elements lighter, deflection of glass due to the ITOstress increases. When the mirror element or window size is large,deflection of the glass can be several millimeters. With traditionalhigh volume production processing, as the thickness of the ITO isincreased the deflection of the substrate typically increases.

Deflection of the glass can be expressed in various ways. One way is toconsider the deflection of the glass is in terms of a lens. Themagnification value then directly relates to the deflection of the glassand is independent of the dimensions of the glass. The magnificationvalues relate to a radius of curvature using the following formula:radius of curvature=(3124 mm)/(1−1/magnification). A perfectly flatpiece of glass will have a magnification value of 1.0. Coated glass,viewed from the coated side, when the coating is in compressive stressthen the glass will become convex on the coated side. If the coatingwere in tensile stress the glass will be concave on the coated side. Acompressive coating results in a warp or magnification value less thanone and conversely if the coating is tensile, the magnification or warpvalues will be greater than 1. Warp values on the order of 0.85 arehighly distorted from flat and glass. Warp values on this order willyield an EC mirror or window that may have double image since thereflectance from the first and third surfaces may not overlap.Additionally, it is difficult to produce a viable seal with glass havingunacceptable warp. Glass with warp values as high as 0.97 can causeissues in manufacturing or with regard to double image.

With reference to FIG. 12, labeled “Argon Pressure Tests,” the warpvalues were measured for ITO coatings on 1.6 mm glass. The glassthickness plays a significant role in deflection and warp when an ITO orother stressed coating is applied. The deflection amount generallyvaries inversely with the cube of the thickness of the glass (assumingthat the intrinsic stress in the coating is constant with thickness ofthe coating). Therefore, thinner glass will warp in a non-linear fashionrelative to thick glass. Thinner glass will generally warp with thinnerITO coatings when compared to thicker glass. The amount of warp scaleslinearly with the thickness of the coatings. In FIG. 12 the coatingswere all approximately 50 nm in thickness. To calculate the warp atother thickness values the following formula may be used: Newwarp=[1−(1−warp value)*new thickness/old thickness]. Applying thisformula to a value in FIG. 12 of 0.98, a warp value of 0.94 for an ITOcoating 150 nm thick and a warp value of 0.74 for a coating 650 nm thickwould be derived. If the glass were thinner these values would deviatefrom flat much more substantially.

FIG. 12 depicts several key findings. First, the warp values or stress(y-axis) in the ITO produced at 2.1 mT do not change substantially overthe oxygen flow rate range (x-axis) in this experiment. Over this rangethe ITO passes through the minimum sheet resistance and bulk resistancevalues. It could be incorrectly concluded that it is not possible tosimultaneously optimize both the electrical and stress properties, notto mention the other required optical properties. At very high oxygenflow rates, warp values start to deviate even more substantially fromflat.

At the higher pressures (4.0 mT) a trend emerges. At low oxygen flowrates the stress in the ITO coating is reduced. But at higher pressuresthis translates into lower oxygen percentages in the overall sputteringenvironment. It is common in the sputtering art to keep the oxygenpercentage constant while adjusting pressure. The trend and findingsleading to one embodiment of the present invention is thereforeundiscovered when traditional experimentation is employed. At the higherArgon pressure of 4 mT depicted with line 1202 a strong trend emergeswhereby the stress in the ITO is minimized at low oxygen flows ascompared to line 1201. The lower stress is due to a uniquemicrostructure or morphology in the ITO coating that is described indetail below. At higher oxygen flow rates the warp values deviate fromflatness, however at any particular oxygen flow rate the warp valuesremain higher than those obtained at the lower pressure. This trendcontinues for even higher pressures than those demonstrated in this FIG.12. The benefits continue at pressures in excess of 7 mT. Furtherimprovements may also be attained at even higher pressures, however,limitations in a particular sputtering chambers may restrictexperimentation at pressures beyond this value.

The graph of FIG. 13 illustrates the effects of a relative increase inArgon pressure and oxygen flow on bulk resistance. This particular testwas conducted utilizing an argon as the sputtering gas. The 400 sccmargon case (line 1301) yields a pressure of 3.7 mT, 550 sccm (line 1302)yields 5 mT, 700 sccm (line 1303) yields 6.2 mT and 850 sccm (line 1304)yields 7.4 mT. The oxygen flow rate on the x-axis is in sccm. It isnoted that significant improvements are obtained with respect to bulkresistivity as Argon pressure and oxygen flow increase. Additionally,the lower Argon pressure cases tend to have a minimum at higher bulkresistance values relative to the higher pressure cases. For reference,a comparable coating made at a pressure of 2 mT comprises a bulkresistance value between about 180 and 200 micro-ohm cm. In a recentlypublished patent application, it was submitted by another manufacturerof electrochromic devices that the current state of the art for ITOcoatings in EC applications corresponds to a bulk resistance of 200micro-ohm cm. This indicates that the benefits and properties of ITOviable for EC applications does not anticipate the improved ITO coatingsof the present invention. The higher pressure cases described herein donot attain their minimum value at the range of oxygen tested.

The graph of FIG. 14 illustrates that higher pressures further result ina relatively thinner ITO coating on the substrate. This fact alsocontributes to why this embodiment of the present invention has not beenpreviously attained. As depicted, when oxygen flow and Argon pressureare increased, the thickness of the ITO coating is decreased. The bulkresistance, an intrinsic measure of the quality of the ITO's electricalproperties, is the multiplication of the sheet resistance and thethickness. It is common to only measure the sheet resistance, however,much information is lost when the coatings are not characterized indetail. Because the coatings are getting thinner with the changes to theprocess gasses the sheet resistance does not follow the same trends asthe bulk resistance. The continued benefits to the bulk resistanceobtained with the higher Argon pressures (line 1404 representing thehighest relative to lines 1401, 1402 and 1403) and oxygen flows areshown in a comparable analysis of the sheet resistance. If only sheetresistance is examined then one may conclude that the 3.7 mT case isbest and the preferred properties are attained at relatively low oxygenflow rates. Another benefit that comes with the lower bulk resistance isthat the real part of the refractive index is reduced. A half wavecoating with a lower refractive index is physically thicker than onewith a higher refractive index resulting in even lower sheet resistance.

The graph of FIG. 15 illustrates the effect of utilizing an argon gas inconjunction with increased Argon pressure and increased oxygen flows,while the graph of FIG. 16 illustrates achieved ITO half wave bulkresistance. In order to attain ½ wave coating two process chambers wereused. The 200 sccm case represents the standard in prior ITO coatings inthe EC art. The half wave coating of the prior art had a sheetresistance of over 12.5 ohms/sq while higher pressure cases inaccordance with at least one embodiment of the present inventionattained values lower then 12 ohms/sq and some even below 11 ohms/sq.Substantial improvement in bulk resistance attained at higher pressuresis exemplified in FIG. 16. In this case oxygen was not optimized at thehigher pressures and the bulk resistance is seen to remain relativelyconstant with argon flows from 400-800 SCCM.

Bulk resistance of the ITO is important, however, as mentioned elsewhereherein sheet resistance is the primary factor that affects darkeningspeed in an EC element. A bulk resistance of 200 micro-ohm cm equates toa sheet resistance of 13.7 ohms/sq for a half wave coating, a bulkresistance of 180 equates to a sheet resistance of 12.4 ohms/sq and abulk resistance of 140 equates to a sheet resistance of 9.6 ohms/sq. 9.6ohms/square is a 30% reduction compared to the 13.7 ohms/sq case andresults in substantial improvements in darkening times and will alsoenable novel bus configurations as described elsewhere herein which alsoimprove element darkening uniformity.

In the next example, coatings were produce in a different coater. Thiscoater has a cathode that is approximately 27 inches long. Theexperiments were conduced with both argon and krypton at a pressure of2.73 millitorr. The coatings were made in two passes past the cathode.The oxygen was varied as depicted in the associated Figs. and tables.The resulting ITO coatings are approximately 600 nm in thickness. InFIG. 17 the absorption (y-axis) in the coatings is plotted as a functionof the oxygen flow rate (x-axis). As can be seen the samples made withKrypton (line 1701) are higher in absorption at a given oxygen flow ratecompared to the samples produced using argon (line 1702) as thesputtering gas.

In FIG. 18 warp in the glass (y-axis) is plotted as a function of oxygenflow rate (x-axis). It can be seen that the samples produced withKrypton (line 1801) have warp values closer to 1 which indicates thatthe krypton produced ITO coated glass is flatter than argon (line 1802)produced glass. FIG. 18 illustrates the data presented earlier where thewarp was shown to increase with increasing oxygen flow rate.

In FIG. 19 warp of the glass (y-axis) is plotted versus the absorption(x-axis). The Krypton produced samples (line 1901) have more absorptionwhen plotted against oxygen flow rate, however, when the warp iscompared against absorption the Krypton produced samples are flatterthan the argon produced samples (line 1902).

FIG. 20 depicts warp (y-axis) versus transmittance (x-axis) for Krypton(line 2001) and Argon (line 2002). Flatter glass is obtained for a givenincreased transmittance value. Additional improvements are possibleusing Krypton or Xenon, or even Argon, at higher pressures. Higherpressures enable the simultaneous achievement of lower stress, highertransparency and lower sheet resistance.

The morphology, or surface features, of the ITO coating also change withpressure and oxygen flow rate. There exists an interaction effectbetween these values where different morphologies are attained atdifferent oxygen flow rates when the pressure is changed. ITO coatingsamples depicted in FIGS. 21-23 were produced in a coater with 72″cathodes. All samples were made at 2.1 mT, 5 kw per target, 1 processchamber (2 targets/side) and a line rate of 32 ipm. The oxygen flow ratewas 2, 8 and 17 sccm for the samples in FIGS. 21, 22 and 23,respectively. Samples of FIG. 21 and FIG. 23 illustrate the extremes inthe morphology. The sample of FIG. 21 has what we call a nodular 2101morphology while the sample of FIG. 23 has a platelet 2302 morphology.Examining the sample of FIG. 21 reveals a background platelet 2102structure. The sample of FIG. 21 is considered to have a somewhat mixedmorphology. The sample of FIG. 22, at the intermediate oxygen flow hasvery few nodules 2201 and an overall dominant platelet 2202 morphology.The platelet morphology has been correlated with a higher stress in thecoatings while the nodular morphology occurs in the coatings with lessstress. Depending on the given process gas pressure, the transitionbetween these two different morphologies is either abrupt or gradual.The low oxygen nodular morphology is characterized by a largepeak-to-valley roughness (as described in detail with regard to FIGS. 33a and 33 b). The nodules rise substantially above the surface of thecoating thus creating large peak to valley roughness. As the nodulestransition into the platelet microstructure the roughness of the surfacedecreases. The roughness is at a minimum when the nodules have justvanished from the surface. At this point we have a plateletmicrostructure with shallow “cliffs” 2103, 2203, 2303 or regions betweenthe platelets. As the oxygen flow is further increased the height of thecliffs between the platelets increases, undesirably increasing theroughness of the surface.

The samples of FIGS. 24-26 are made at comparable powers and line ratesas with those of FIGS. 21-23 and all at 2 sccm oxygen. The process gaspressures were 3.7, 2.1 and 1.6 millitorr respectively. The morphologyis increasingly dominated by the nodular morphology as the pressure isincreased. The transition between the nodular 2401, 2501, 2601 andplatelet morphologies is more gradual at the higher pressures, thus,allowing a finer adjustment between desirable optical and mechanicalproperties in the coating. The platelet 2402 morphology is still presentin the background of the 3.7 millitorr sample, however, in a much lessdominant amount. As the pressure is further decreased the nodulecomponent is eventually eliminated leaving only the platelet morphology.

Use of Krypton or other heavier sputtering process gas is similar insome regards to running at a higher pressure. Three SEM images of ½ waveITO samples are compared which were produced with Krypton as the processgas and with varying oxygen flow rates as depicted in FIGS. 27-29. Thesesamples are described in more detail with reference to Table 6. Thesesamples were made at 40 ipm line rate and 6.2 kw and using two processchambers (four cathodes/side). The glass thickness was 1.1 mm. Oxygenflow rates are 8, 12 and 16 sccm for samples in FIGS. 27, 28 and 29,respectively. The oxygen flow rates are per process chamber. The surfaceof the sample depicted in FIG. 27, produced at 8 sccm oxygen, hasvirtually no platelet component and is extremely stress free; thesurface of this sample is predominantly nodules 2701. The sampledepicted in FIG. 27, and the other ½ wave samples from Table 6, has warpvalues that are essentially unity. The surface structure of the sampledepicted in FIG. 28 is generally comprised of nodules 2801 and has avery minor amount of platelet 2802 morphology with slight cliffs 2803.The sample of FIG. 29 is essentially all platelet 2902 surface structurewith well defined cliffs 2903. The samples have very low bulk resistancevalues of approximately 150 micro-ohm cm. The absorption of thesecoatings is fairly low with the 12 sccm case having the best combinationof flatness, resistivity and absorption. The low stress values for thesecoatings indicates that even some platelet morphology can be utilizedwith success when produced using higher pressures or with heaviersputtering gasses.

samples D, E and F as depicted in FIGS. 30-32, respectively, are for the2-wave ITO cases as tabulated in Table 7 and correspond to the 8, 12 and16 sccm flow rates, respectively. The line rate was 7 ipm for thesesamples otherwise the process conditions were equivalent to those ofTable 6. These coatings are approximately 5 times thicker than theirhalf wave counterparts. The morphology of the coatings is somewhatdifferent on these samples with the nodular 3001, 3101, 3201 morphologyof the thinner samples giving rise to a more granular structure (sampleD, FIG. 30). There are voids between the grains depicted in FIG. 30which gives rise to undesirably high haze and a degraded conductivity;this is exemplified by the relatively high bulk resistance value of 200micro-ohm-cm for this sample. Sample E, made with 12 sccm of oxygen hasa very low bulk resistance (131 micro-ohm cm) and a fine grainmicrostructure. The 16 sccm case has a similar microstructure but inthis case the platelet morphology is not present as it is in the thinnercoatings. The stress levels of these Krypton-produced coatings arerelatively low. The warp values range from essentially unity for the lowoxygen case to 0.956 for the highest oxygen case. These samples wereproduced with 1.1 mm glass which is more susceptible to warp compared tothe thicker 1.6 mm glass described previously. Still, the warp valuesare very close to unity. This is with coatings that are over 10 timesthicker than the 50 nm coatings originally discussed on 1.6 mm glass.Not only do these coatings have extremely low stress but they also havebetter bulk resistance values and acceptable absorption values.

The peak-to-valley surface roughness (as defined in the discussion belowwith reference to FIGS. 33 a and 33 b) for these coatings is preferablyless than or equal to 200 Å, more preferably less than 150 Å, morepreferably less than or equal to about 100 Å, even more preferably lessthan or equal to about 50 Å, and most preferably less than or equal toabout 25 Å.

To illustrate additional features and advantages of an electrochromicmirror, constructed in accordance with at least one embodiment of thepresent invention, summaries of experimental results are provided belowin tables 3 and 4. In these summaries, references are made to thespectral properties of elements of electrochromic mirrors constructed inaccordance with the parameters specified in each example. In discussingcolors, it is useful to refer to the Commission Internationale deI'Eclairage's (CIE) 1976 CIELAB Chromaticity Diagram (commonly referredto a the L*a*b* chart). The technology of color is relatively complex,but a fairly comprehensive discussion is given by F. W. Billmeyer and M.Saltzman in Principles of Color Technology, 2^(nd) Edition, J. Wiley andSons Inc. (1981), and the present disclosure, as it relates to colortechnology and terminology, generally follows that discussion. On theL*a*b* chart, L* defines lightness, a* denotes the red/green value, andb* denotes the yellow/blue value. Each of the electrochromic media hasan absorption spectra at each particular voltage that may be convertedto a three number designation, their L*a*b* values. To calculate a setof color coordinates, such as L*a*b* values, from the spectraltransmission or reflectance, two additional items are required. One isthe spectral power distribution of the source or illuminant. The presentdisclosure uses CIE Standard Illuminant A to simulate light fromautomobile headlamps and uses CIE Standard Illuminant D₆₅ to simulatedaylight. The second item needed is the spectral response of theobserver. The present disclosure uses the 2 degree CIE standardobserver. The illuminant/observer combination generally used for mirrorsis then represented as A/2 degree and the combination generally used forwindows is represented as D₆₅/2 degree. Many of the examples below referto a value Y from the 1931 CIE Standard since it corresponds moreclosely to the spectral reflectance than L*. The value C*, which is alsodescribed below, is equal to the square root of (a*)²+(b*)², and hence,provides a measure for quantifying color neutrality.

Tables 3 and 4 summarize experimental results for elements constructedin accordance with the present invention. Specifically, experiments wereconducted within a range of between 8 sccm and 16 sccm oxygen flow forboth half and two wave thicknesses with krypton as the sputtering gasand at a pressure of 3 mTorr. Table 6 summarizes the results for aslightly less than half wave ITO thickness, while Table 7 summarizes theresults for a slightly more than two wave ITO thickness, the half wavethickness being applicable, for example, to mirror applications and thetwo wave thickness being applicable, for example, to windowapplications. Further, it is noted that these tables include results forboth single layers and elements constructed of dual layers.

TABLE 6 Experiment Rack Singles Average Ab- Re- Oxy- Oxy- Transmittancesorp- flec- Cell gen ohms gen Trial L* a* b* Y Haze Singles L* a* b* YHaze tion tion Absorption  8 11.6  8 1/2wv-8sccm-1/3 93.1 −2.8 4.7 83.30.06 .5W 8-1 94.9 −2.1 3.8 87.3 0.01 4.1 8.5 8.7 .5W 8-3 94.8 −2.1 3.887.2 0.01 4.3 8.5 1/2wv-8sccm-2/4 92.9 −2.6 5.7 82.8 0.01 .5W 8-2 94.7−1.9 4.9 86.9 0.02 4.5 8.6 9.1 .5W 8-4 94.7 −1.9 5.2 86.9 0.01 4.3 8.810 10.9 10 1/2wv-10sccm-1/3 93.4 −2.7 5.7 83.9 0.01 .5W 10-1 95.0 −2.15.0 87.5 0.02 3.5 8.9 7.6 .5W 10-3 94.8 −1.8 5.6 87.2 0.01 3.7 9.11/2wv-10sccm-2/4 93.8 −3.0 4.2 84.9 0.02 .5W 10-2 95.1 −2.3 4.0 87.90.00 3.2 8.9 6.9 .5W 10-4 95.1 −2.3 2.9 88.0 0.01 3.2 8.8 12 10.6 121/2wv-12sccm-1/2 94.1 −3.1 4.2 85.5 0.05 .5W 12-1 95.2 −2.4 3.9 88.20.01 2.9 8.9 6.3 .5W 12-2 95.3 −2.4 2.9 88.3 0.01 2.7 9.0 14 11.1 141/2wv-14sccm-2/4 94.3 −3.1 4.1 85.9 0.05 .5W 14-2 95.3 −2.4 3.5 88.30.01 2.7 9.1 5.8 .5W 14-4 95.3 −2.5 3.1 88.4 0.02 2.4 9.1 16 11.0 161/2wv-16sccm-1/2 94.3 −3.1 4.8 85.9 0.15 .5W 16-1 95.3 −2.5 4.1 88.40.01 2.5 9.1 5.6 .5W 16-2 95.3 −2.5 4.0 88.4 0.01 2.6 9.0 Total Oxy-Reflectance Bulk rough- Thick- Ohms/ Bulk gen Trial L* a* b* Y HazeSingles L* a* b* Y Haze Thick ness ness sq Resistance  8 1/2wv-8sccm-1/333.9 6.1 −12.4 7.9 0.06 .5W 8-1 35.0 8.5 −13.3 8.5 0.01 131.9 5.4 137.311.6 159.3 .5W 8-3 35.0 8.5 −12.9 8.5 0.01 1/2wv-8sccm-2/4 34.4 5.1−16.1 8.2 0.01 .5W 8-2 35.1 7.8 −16.8 8.6 0.02 .5W 8-4 35.6 7.5 −17.48.8 0.01 10 1/2wv-10sccm-1/3 34.9 5.2 −17.0 8.4 0.01 .5W 10-1 35.9 7.8−17.6 8.9 0.02 132.7 5.0 137.7 11.1 152.8 .5W 10-3 36.2 6.4 −19.2 9.10.01 1/2wv-10sccm-2/4 34.3 6.6 −12.4 8.2 0.02 .5W 10-2 35.8 8.8 −14.28.9 0.00 .5W 10-4 35.7 8.6 −10.2 8.8 0.01 12 1/2wv-12sccm-1/2 34.5 6.9−12.4 8.2 0.05 .5W 12-1 35.8 9.0 −14.1 8.9 0.01 130.2 4.4 134.6 11 148.1.5W 12-2 36.0 8.9 −10.5 9.0 0.01 14 1/2wv-14sccm-2/4 34.7 7.2 −12.3 8.40.05 .5W 14-2 36.1 9.1 −12.9 9.1 0.01 127.6 5.1 132.7 11.7 155.3 .5W14-4 36.2 9.2 −11.1 9.1 0.02 16 1/2wv-16sccm-1/2 34.9 7.2 −14.9 8.5 0.15.5W 16-1 36.1 9.3 −15.0 9.1 0.01 126.7 3.6 130.3 11.45 149.2 .5W 16-236.0 9.3 −14.8 9.0 0.01

TABLE 7 Transmittance Singles Cell Oxygen Trial L* a* b* Y Haze SinglesL* a* b* Y Haze Absorption Reflection Absorption  8 2wv-8sccm-1/3 84.0−2.9 4.2 64.0 2.0 2W 8-1 89.0 −0.9 3.8 74.2 1.48 17.5 8.3 27.0 2W 8-388.6 −0.5 5.0 73.3 1.47 18.2 8.5 2wv-8sccm-2/4 84.2 −2.8 4.4 64.4 1.9 2W8-2 88.9 −0.9 4.1 74.0 2.20 16.5 9.5 25.4 2W 8-4 88.6 −0.2 5.0 73.3 1.8716.2 10.5 10 2wv-10sccm-2/4 85.2 −2.9 3.4 66.3 1.7 2W 10-2 89.5 −0.6 3.575.3 1.54 15.3 9.4 24.3 2W 10-4 89.4 −1.0 3.7 75.0 1.51 15.9 9.12wv-10sccm-1/3 85.6 −2.6 3.3 67.1 1.8 2W 10-1 89.8 −0.5 3.6 75.9 1.4115.0 9.1 23.4 2W 10-3 89.5 −0.7 3.4 75.3 1.51 15.5 9.3 12 2wv-12sccm-1/284.5 −2.5 2.4 65.0 0.1 2W 12-1 89.5 −0.5 1.9 75.3 0.22 13.8 11.0 22.5 2W12-2 89.4 −0.9 2.0 75.1 0.20 14.2 10.7 2wv-12sccm-3/4 78.8 −2.8 2.9 54.50.3 2W 12-3 89.6 −1.1 2.3 75.4 0.23 12.6 12.0 35.5 2W 12-4 83.4 −1.0 2.162.9 0.25 13.1 14 2wv-14sccm-1/3 85.3 −2.6 1.8 66.7 0.3 2W 14-1 89.6−0.7 1.4 75.5 0.33 13.6 10.9 23.4 2W 14-3 89.8 −1.1 1.7 75.9 0.27 13.111.0 2wv-14sccm-2/4 84.4 −2.6 1.5 64.9 0.3 2W 14-2 89.3 −0.7 1.2 74.80.38 13.8 11.3 25.5 2W 14-4 89.3 −0.8 1.5 74.8 0.30 14.6 10.7 162wv-16sccm-1/3 86.5 −2.8 1.9 69.0 0.7 2W 16-1 89.7 −1.1 2.2 75.8 0.6310.8 13.4 18.8 2W 16-3 90.3 −1.3 1.0 77.0 0.63 11.0 12.0 2wv-16sccm-2/487.2 −2.8 1.4 70.3 0.7 2W 16-2 90.5 −1.3 1.2 77.4 0.53 10.8 11.8 18.8 2W16-4 90.5 −1.2 1.0 77.4 0.58 10.7 11.9 Data from Center of Rack BulkTotal Re- Reflectance Bulk rough- Thick- sis- Trial L* a* b* Y HazeSingles L* a* b* Y Haze Thick ness ness Ohms tance Warp 2wv-8sccm-1/335.9 −2.4 −3.1 9.0 2.0 2W 8-1 34.6 −1.9 −3.2 8.3 1.48 758.5 21.4 779.92.6 202.8 0.996 2W 8-3 35.1 −2.0 −3.8 8.5 1.47 2wv-8sccm-2/4 38.3 −2.7−5.3 10.3 1.9 2W 8-2 36.9 −2.2 −4.4 9.5 2.20 2W 8-4 38.6 −3.3 −4.9 10.51.87 2wv-10sccm-2/4 36.7 −2.3 −3.5 9.4 1.7 2W 10-2 36.8 −3.1 −2.1 9.41.54 740.9 16.1 757.0 1.95 147.6 0.984 2W 10-4 36.2 −2.2 −1.9 9.1 1.512wv-10sccm-1/3 36.9 −3.1 −2.9 9.5 1.8 2W 10-1 36.3 −2.3 −2.0 9.1 1.41 2W10-3 36.5 −1.7 −2.5 9.3 1.51 2wv-12sccm-1/2 42.1 −5.8 −9.0 12.5 0.1 2W12-1 39.5 −4.5 −6.3 11.0 0.22 705.7 6.2 711.9 1.85 131.7 0.972 2W 12-239.1 −2.8 −6.4 10.7 0.20 2wv-12sccm-3/4 37.8 −4.1 −7.7 10.0 0.3 2W 12-341.2 −1.4 −8.2 12.0 0.23 2W 12-4 42.9 −5.4 −7.2 13.1 0.25 2wv-14sccm-1/337.6 −2.9 −6.4 9.9 0.3 2W 14-1 39.4 −2.9 −4.9 10.9 0.33 712.7 7.2 719.91.95 140.4 0.961 2W 14-3 39.6 −3.4 −4.5 11.0 0.27 2wv-14sccm-2/4 37.1−3.6 −6.1 9.6 0.3 2W 14-2 40.1 −1.2 −5.7 11.3 0.38 2W 14-4 39.1 −3.1−5.3 10.7 0.30 2wv-16sccm-1/3 41.6 −1.3 −7.2 12.2 0.7 2W 16-1 43.4 −0.8−5.9 13.4 0.63 716.5 8.9 725.4 2 145.1 0.956 2W 16-3 41.2 −0.7 −3.5 12.00.63 2wv-16sccm-2/4 39.3 −1.3 −5.0 10.9 0.7 2W 16-2 40.9 −0.6 −3.7 11.80.53 2W 16-4 41.0 −0.7 −3.3 11.9 0.58

Table 8 depicts the inter-dependence between bulk resistance, electronmobility and electron carrier concentration. It is noted that there is acontinuum of carrier concentration and mobility combinations that willyield a given bulk resistance.

TABLE 8 Bulk Resistance Cc mu RI n RI k 160 1.15E+21 34.0 1.776 0.0145160 6.88E+20 56.7 1.8845 0.0054 160 4.91E+20 79.4 1.9295 0.0031 1401.31E+21 34.0 1.7349 0.0168 140 7.86E+20 56.7 1.8616 0.0062 140 5.61E+2079.4 1.9135 0.0034 120 1.53E+21 34.0 1.6791 0.0202 120 9.17E+20 56.71.8306 0.0072 120 6.55E+20 79.4 1.892 0.0039

The electron carrier concentration is preferably greater than or equalto 40 e²⁰ electrons/cc, while the mobility is preferably greater than orequal to 25 cm^2/V-s. The carrier concentration and electron mobility,thickness and surface roughness presented herein are derived fromellipsometric analysis of the coatings. The electron concentration andmobility may vary from those determined using a Hall characterizationmethod and one skilled in the art will recognize that an offset mayexist between the measurement methods. As noted above there are acontinuum of carrier concentrations and mobility values that can attaina given bulk resistance. In an embodiment where a low refractive indexis preferred then tuning of the deposition process to yield a highercarrier concentration will be preferred. In other embodiments where alow absorption is preferred then tuning of the deposition process toyield higher electron mobility will be preferred. In other embodimentsone may desire an intermediate level of both carrier concentration andmobility.

In at least one embodiment, an electro-optic element includes animproved ITO layer that simultaneously exhibits a reduced bulkresistance, reduced absorption, decreasing bending or warping of theassociated substrate to which the ITO is applied, and maintaining auniform darkness and brightness of the overall assembly, and reduces theweight thereof.

surface topology, morphology or roughness is typically not important innon-microscale electrical applications dealing with metal coatings. Thesurface topology is of particular interest when metals are used in anoptical application. When the surface roughness becomes too large thecoating will have appreciable non-specular reflectivity or haze. Thisdegree of roughness, in most applications, is often the first to beaddressed because it can have a negative impact on visual appearance butnot necessarily on functionality. In the case of optical applications,such as many described herein, the presence of objectionable haze isconsidered a worst case scenario. The surface roughness may have othernegative consequences at roughness levels much less than those thatresult in objectionable haze. Surface roughness levels define acceptablemorphologies for metal films to allow them to function adequately indifferent optical applications. A penalty associated with not adequatelycontrolling the surface morphology is often increased cost since largerquantities of higher priced metals with higher reflectivity are oftenneeded overcome the problems associated with improper surfacemorphology. The effects of different levels of morphology or surfaceroughness using thin film modeling techniques have been analyzed. Thesetechniques are accepted in the art of thin film technologies and havebeen proven to accurately describe real thin film or coating systems andcan therefore be used to predict the impact of different changes to acoating. This is advantageous because it may be expensive or timeconsuming to manufacture or fabricate the large number of samples neededto show the effects. In this case a commercial thin film program calledTFCalc supplied by Software Spectra, Inc. was used to perform thecalculations.

The roughness, as used herein, is defined in terms of meanpeak-to-valley distance. The FIGS. 33 a and 33 b depict two differentroughness scenarios. In FIG. 33 a large crystallites 3302 a arerepresented. In FIG. 33 b small crystallites 3302 b are represented. Inboth of these cases the peak-to-valley distance 3301 a, 3301 b isdepicted to be the same. Additionally, both examples have the same voidto bulk ratios. It should be understood that the valleys and peaks maynot be at the same height. The mean peak-to-valley measurement,therefore, provides a more representative quantifying value.

When the layer is thin it may be approximated by a single homogeneouslayer with a uniform refractive index. There are several ways toapproximate the refractive index of a mixed layer. These are calledeffective medium approximations (EMA). Each different EMA has itsstrengths and weaknesses. In these examples a Bruggeman EMA methodologywas employed. When the thickness of the layer becomes large theroughness is not approximated well if a single fixed refractive index isused. In these cases the roughness may be approximated as several slicesof different ratios of void and bulk material to form a graded indexapproximation.

several metals are modeled herein to provide representative examples ofthe optical effect of surface roughness on reflectance. Tables 9, 10,and 11 show the effect of roughness thickness on the reflectivity of thesurface for Ag, Cr and Rh, respectively. The thickness of the layers isin nanometers and the Cap Y value represents the reflectance from thecoated surface. The reflectivity drops off as the thickness of theroughness increases for each of these metals. Depending on theapplication, the amount of acceptable roughness will vary. The roughnessshould be less than 20 nm mean peak-to-valley, preferably less than 15nm, even more preferably less than 10 nm and even more preferably lessthan 5 nm and most preferably less than 2.5 nm. These preferred ranges,as noted above, depend on the application. For instance, in oneembodiment, the thickness of a flash layer, cover layer, barrier layeror adhesion layer (i.e., functional layer) may need to scale with thedegree of roughness of the underlying surface. The thickness of thefunctional layer necessitated by the roughness of the underlying surfacemay result in undesirable effects such as changes in optical propertiesof the resultant stack, higher costs or other negative effects. Means tosmooth the surfaces prior to deposition of the functional layers aredescribed below. It should be noted that there may be some embodimentswhere increased surface roughness may be advantageous such as creatingan effectively larger surface area for better adhesion to a sealmaterial.

The tables 9, 10, and 11 also include a value labeled as “% ofTheoretical Maximum”. This metric defines how close the reflectance of acoating with a rough surface matches the reflectance of the ideal,perfectly smooth surface. A coating with a % of Theoretical Maximumvalue of 100% would have the maximum reflectance theoreticallyattainable for that material. If the % of Theoretical Maximum value was85% then the reflectance attained would be only 85% of the value of theideal smooth coating or reflectance of coating with zero roughness times0.85.

The reflectance of a metal or alloy coating is dependent on manyattributes of the coating even one that is relatively smooth. Thedensity of the coating, presence or absence of internal voids, stresslevels, etc all play a role in how the reflectance approaches some idealmaximum value. The theoretical maximum reflectance defined hereinpertains not to this ideal reflectance of an ideal coating but rather tothe reflectance value of a smooth real world coating. In practice theTheoretical Maximum value is obtained through a combination of opticalanalysis and thin film modeling. By analyzing a real world coating thathas surface roughness using an optical technique such a Variable AngleSpectroscopic Ellipsometry the refractive index versus wavelength andsurface roughness can be obtained. The refractive index versuswavelength can then be inputted into a thin film modeling program suchas TFCalc or Essential Macleod and the reflectance can be calculated.This calculated reflectance using measured refractive index data is thenthe Theoretical Maximum reflectance value from that particular film orcoating.

Preferably the reflectance of a coating is greater than 85% of theTheoretical Maximum, more preferably 90% of the Theoretical Maximum andmost preferably greater than 95% of the Theoretical Maximum.

TABLE 9 Effect of roughness thickness on reflectivity of Ag coatingsSilver % of Theoretical Bulk Roughness Cap Y Maximum 350 0 98.5 350 595.2 97% 350 10 91.3 93% 350 15 87.1 88% 350 20 82.7 84% 350 25 78.4 80%350 30 74.2 75% 350 35 70.4 71% 350 40 66.8 68% 350 45 63.6 65% 350 5060.8 62% 350 55 58.3 59% 350 60 56.2 57%

TABLE 10 Effect of roughness thickness on reflectivity of chromecoatings Chrome % of Theoretical Bulk Roughness Cap Y Maximum 40 0 65.940 5 64.6 98% 40 10 62.2 94% 40 15 59.0 89% 40 20 55.2 84% 40 25 51.378% 40 30 47.7 72% 40 35 44.5 68% 40 40 41.9 64% 40 45 39.8 60% 40 5038.3 58% 40 55 37.2 56% 40 60 36.5 55%

TABLE 11 Effect of roughness thickness on reflectivity of rhodiumcoatings Rhodium % of Theoretical Bulk Roughness Cap Y Maximum 40 0 76.940 5 74.8 97% 40 10 71.6 93% 40 15 67.2 87% 40 20 62.1 81% 40 25 56.473% 40 30 50.7 66% 40 35 45.2 59% 40 40 40.3 52% 40 45 36.0 47% 40 5032.4 42% 40 55 29.6 38% 40 60 27.4 36%

In some applications it is desirable to have high second surfacereflectance where the reflectance is off of the metal layer when viewedthrough the glass. In this case buried void is of concern in addition tosurface roughness. The amount of void (% relative to bulk) may vary andthe thickness of the void layer may vary also. The general rulesdescribed above for surface roughness apply here as well.

Often times when metallic layers comprise low sheet resistance surfaceroughness is of particular concern. A metal or other electricallyconductive material has an intrinsic property known as the bulkresistivity. The sheet resistance of the coating is determined bydividing the bulk resistance number by the thickness of the coating. Inprinciple, any sheet resistance value can be obtained from anyconductive material as long as the coating is thick enough. Thechallenge or limitation in achieving low sheet resistance comes in whenother attributes are required in addition to the sheet resistance orconductivity.

As the thickness of coatings is increased the surface roughnesstypically also increases which leads to a reduction in the specularreflectivity as described previously. Coatings which are very thickoften have reflectivity levels significantly below those of a perfectlysmooth surface. The amount of roughness a coating will develop is afunction of a number of factors. The properties of the material itselfare the major driving force but within boundaries the deposition processparameters (along with which deposition process is employed) can modifythe surface properties of the coating.

Due to other considerations, the material with the best surfaceroughness can not always be selected for a given application. Otherfactors also play a role. Adhesion and cost, for instance, are criticalissues which influence the selection of materials which go into acoating stack. Often it is impossible to select a single material tomeet all of the requirements; therefore, multilayer coatings areemployed. Certain platinum group metals have high reflectivity such asRhodium, Ruthenium, Iridium, etc but are very expensive. Therefore, anentire coating with a low sheet resistance produced with these materialswould be cost prohibitive. When extreme adhesion to glass or othermaterials may be needed then these materials may also be found to haveweaker bond strengths than other materials. Silver based coatings mayhave insufficient stability as an anode and depending on the coatingstack may also be problematic from an adhesion standpoint. A metal suchas chrome is relatively low in cost compared to some other metals and isknown to have very good adhesion. Chrome may, therefore, function as anadhesion layer and may be built up to sufficient thickness to get thedesired electrical properties.

Unfortunately, chrome is very reactive and this leads to an intrinsicpredisposition to relatively large surface roughness values. The highreactivity is important in that as the coating is deposited, usingMagnetron Sputter Vacuum Deposition (MSVD) for example, the chrome atomswill tend to stick where they first land. The rate of bond formation isvery fast and this restricts the atom's ability to diffuse along thesurface and find a low energy location. Typically, a low energy stablelocation on the coating is one that lends itself to less surfaceroughness. This tendency to not go to a low energy state alsocontributes to a degradation of the coating's bulk resistance.Therefore, a thicker layer is needed to attain the target sheetresistance and the surface roughness tends to further degrade. It isdifficult to simultaneously attain the goal of low sheet resistance andhigh reflectivity because of these competing effects.

It is known that the reflectivity of a low reflectance metal may beincreased by putting a thin layer of a higher reflectance metal aboveit. For instance, the previously mentioned metals such as Rhodium orRuthenium may be used. The necessary thickness of these metals to attaina given reflectivity level will be a direct result of the surfaceroughness of the underlying chrome layer. Other metals that could beused as the conductive layer include, but are not limited to, aluminum,cadmium, chromium, cobalt, copper, gold, iridium, iron, magnesium,molybdenum, nickel, osmium, palladium, platinum, rhodium, ruthenium,silver, tin tungsten and zinc. Alloys of these metals with each other orwith another metal or metals may be possible. The suitability of thesematerials in a given application will depend on the full list ofrequirements. For instance, Ruthenium may be an expensive metal in oneapplication but in another application it may be low cost relative toanother metal such as Rhodium and may therefore fall within the spiritof this invention. In other non-limiting embodiments a given metal oralloy may not be compatible with all of the other components in anapplication. In this case, the sensitive metal may be buried orotherwise isolated from components where there are interactionlimitations. The layers deposited on top of the chrome usually willpattern the roughness of the underlying layer. Therefore, a thin layerof a higher reflectance metal will also not have its ideal reflectivitybecause of the layer or layers underneath it. In most instances thepreferred embodiment is one that has the higher reflectance metaloriented toward the observer. Many of the high conductivity metalslisted above also have high reflectivity. These metals may need to bealloyed with other metals to have adequate chemical, environmental orphysical properties. The metals or alloys may then have an unacceptablecolor or hue. The overall reflectance intensity may be adequate for thedesired application but if the reflected color does not meetrequirements then the metal or alloy is unsuitable. In this case,similar to the description above, the metal or alloy may be buriedbeneath a layer with lower intrinsic reflectivity but one that has amore preferable reflected color.

Reference samples were prepared to allow evaluation of the trade-offbetween reflectance and sheet resistance for a chrome-ruthenium bi-layercoating stacks. In these samples chrome was applied to get a targetsheet resistance value. The samples were then overcoated with Rutheniumof different thicknesses. The following process conditions wereemployed:

All of the coating were processed a 3.0 mTorr

Cr @ 4.0Kw @ (130)=approx 1000 angstroms

Cr @ 4.0Kw @ (130)×9=0.7 ohms squ.

Cr @ 4.0Kw @ (130)×3=1.5 ohms. squ.

Cr @ 4.0Kw @ (87)×1=3 ohms squ.

Cr @ 4.0Kw @ (170)×1=6 ohms squ.

Ru @ 1.7Kw @ (130)=400 angstroms

Ru @ 0.85Kw @ (130)=200 angstroms

Ru @ 0.43Kw @ (130)=100 angstroms

Ru @ 0.43Kw @ (260)=50 angstroms

Ru @ 0.43Kw @ (520)=25 angstroms

The chrome samples were all deposited at 4 kw. The line speed (inparenthesis—arbitrary units) and number of passes (e.g. ×9) were variedto adjust the thickness of the coating to hit sheet resistance targets.The ruthenium layers were produced with varying line speed and power toattain the target thickness levels. The results of the matrix aretabulated in Table 12. The reflectivity generally drops with increasingthickness and decreasing sheet resistance. Several samples preparedwhich target 3 ohm/sq do not fit the trends. This is because they weremade a different line speed than the other chrome coatings. When theline speed is reduced the substrate moves at a slower speed. In a linearprocess this means that the initial nucleation layers are formedpredominantly with sputtered high angle deposition materials. As notedin the description below, the high angle deposition results in inferiormaterial properties. Shielding is often used to eliminate this highangle deposition. The 3 ohm/sq chrome case in this study is an excellentexample of how the high angle can degrade the optical properties of thecoating.

TABLE 12 Chrome Ruthenium bi-layer results Haze (Specular TrialRuthenium Ohms Y a* b* Excluded) #1 .7 0 0.6 50.0 −0.9 0.0 0.13 #2 1.5 01.5 55.3 −0.7 −0.2 0.04 #3 3 0 2.9 54.4 −0.5 0.5 0.02 #6 6 0 5.1 60.9−0.9 −0.2 0.02 #1 .7 25 25 0.6 50.7 −0.9 1.0 0.11 #2 1.5 25 25 1.6 54.2−0.6 0.8 0.03 #3 3 25 25 3 53.0 −0.5 1.1 0.02 #4 6 25 25 5.9 58.8 −0.71.0 0.02 #1 .7 50 50 0.6 51.0 −0.9 1.6 0.12 #2 1.5 50 50 1.5 55.0 −0.61.2 0.03 #3 3 50 50 2.9 54.1 −0.5 1.2 0.03 #6 6 50 50 5.6 59.6 −0.6 1.20.02 #1 .7 100 100 0.6 52.7 −0.7 2.4 0.13 #2 1.5 100 100 1.5 56.6 −0.51.6 0.04 #3 3 100 100 2.8 56.7 −0.4 1.3 0.03 #6 6 100 100 5 62.5 −0.41.2 0.02 #1 .7 200 200 0.5 54.7 −0.2 2.7 0.14 #2 1.5 200 200 1.4 60.1−0.1 1.6 0.04 #3 3 200 200 2.5 63.1 0.0 1.3 0.03 #6 6 200 200 4.2 67.4−0.1 0.9 0.03 #1 .7 400 400 0.6 56.5 0.2 2.6 0.15 #2 1.5 400 400 1.364.1 0.1 1.4 0.05 #3 3 400 400 2 67.5 0.0 1.2 0.03 #6 6 400 400 3 69.8−0.1 0.8 0.03

As can be seen from Table 12, the chrome coating alone has relativelylow reflectance values even at the 6 ohm/sq case. The reflectance wasonly about 61% for this sample. Chrome produced by other means orprocess conditions should be able to attain values in excess of 65%.Therefore, even at this modest sheet resistance value the chromereflectance has been compromised.

When a 3 ohm/sq coating is desired, 100 and 200 angstroms of rutheniumon top of the chrome is needed to attain even modest reflectance values.Ideally, a ruthenium coating should be able to attain a reflectance inexcess of 72%. Even 400 angstroms on top of the 6 ohm/sq chrome fallshort of the theoretical optimum by 2%. The lower ohm samples do noteven come close to approaching the theoretically attainable reflectancevalues. Therefore, in cases where both low sheet resistance and highreflectance are needed a standard chrome-ruthenium bi-layer does notmeet the requirements. Other means must be employed to solve thisproblem.

Deposition process parameters can be adjusted to minimize the surfaceroughness during the formation of the coating. In the case of metals,the surface roughness can be reduced and the reflectivity increased byrunning the process at low pressure and preferably using neon or anargon-neon mixture as the sputtering gas as described in detail below.These parameters contribute to proper momentum and energy transfer inthe deposition process with the result in less rough surfaces and lowerbulk resistivities.

Table 13 depicts how the surface roughness, reflectivity and electricalproperties vary as the process parameters are adjusted. The 3 mT case isprovided as a reference. The thickness of the coating is about 600angstroms. This thickness is important because the coating is nearlyopaque at this level and the sheet resistance is relatively low. As canbe seen, lowering the pressure reduces the roughness by about 17% andalmost a 2% increase in reflectance is achieved. Lowering the pressureand sputtering with a 50:50 mixture of argon and neon results in furtherimprovements. The roughness is about 20% lower than the reference caseand the reflectance is about 2.7% higher. The last case is with evenhigher amounts of neon—approximately 70% of the sputtering gas is neon.Reflectance is about 3.5% higher than in the reference case and theroughness is reduced by about 24%. Thickness and roughness values aredetermined by using variable angle spectroscopic ellipsometry.

TABLE 13 Chrome properties versus process settings Chrome BulkResistance Sheet Micro- Reflec- Process Thickness Roughness Resistanceohm tance Conditions Angstroms Angstroms Ohms/sq cm % 3 mT Chrome 484101 13.5 79 59.6 100% Ar 2 mT Chrome 494 84 12.6 72.8 61.7 100% Ar 2 mTChrome 507 81 11 64.7 62.3 50:50 Ar:Ne 2 mT Chrome 506 77 11.3 65.9 63.110:24 Ar:Ne

Results can be further improved by lowering the pressure and byincreasing the neon content in the sputtering gas. In addition,increasing the substrate temperature also contributes to smoothercoatings. Higher substrate temperature results in more surface mobilityof the deposited atoms leading to a smoother surface.

Table 13 also includes bulk resistance values for the chrome coatings.The theoretical minimum bulk resistance value for chrome is about 13micro ohm cm. The reference case made at a typical pressure of 3 mT inargon has a bulk resistance value of more than 6 times the theoreticalbulk resistance. By improving the deposition properties bulk resistancevalues of less than 5 times the theoretical minimum may be obtained.Preferably, the bulk resistance is less than 5 times the theoreticalminimum, more preferably less than 4 times the theoretical minimum, morepreferably less than 3 times the theoretical minimum and most preferablyless than 2 times the theoretical minimum.

The presence of oxygen (or water) in the system can be particularlyharmful from a surface roughness perspective. Chrome is very reactivewith oxygen and tends to react immediately. This leads to additionalroughness in the coating. Therefore, a coating with less oxygen isrecommended. Table 14 depicts the effect of oxygen on roughness. Theoxygen level in Table 14 refers to the percentage in the sputtering gas.The pressure is in mT and the thickness is in angstroms. The amount ofacceptable oxygen in the coating is less than 5 atomic percent,preferable less than 2 atomic percent and ideally less than 1 atomicpercent.

TABLE 14 The effect of oxygen percentage in the sputtering atmosphere onthe roughness of chrome coatings Oxygen level pressure thicknessRoughness 1 2.00 493 105 5 2.00 438 130 10 2.00 370 162

The amount of acceptable roughness is dependent on the application. Whenhigh reflectance values are desired less roughness is also desirable.Where reflectance requirements are not as stringent more roughness maybe acceptable. Generally, roughness should be less than about 200angstroms, preferable less than 100 angstroms, even more preferably lessthan 50 angstroms, even more preferably less than 25 angstroms and mostpreferably less than 15 angstroms. Roughness as the term is used hereinrefers to the average peak-to-valley distance as determined usingellipsometry or atomic force microscopy.

Other means may be used either alone or together with each other or thepreviously mentioned methods to minimize surface roughness. For example,the cathode may be shielded to minimize the grazing (high) angledeposition. Other methods to get smoother surfaces include the use ofion assisted sputtering or ion assisted deposition, plasma assistedsputtering and other means to increase surface mobility of atoms. Thecathode type may be selected to facilitate smoother coatings, such as,use of “twin mags”, unbalance magnetrons, rf superimposed dc power,microwave assisted sputtering, high power pulse deposition, ACsputtering or other such means.

Although Chrome was used in the examples above as the conductive layer,other metals, alloys or multilayer coating materials as described hereinand within the references incorporated herein may be used within thespirit of the invention. Other materials may need other processconditions to attain smooth surfaces. ITO for instance does notnecessarily have smooth surfaces under conditions which are preferredfor metals. In the case of ITO, the surface morphology is modified by anumber of process variables. The case of controlling the surfaceproperties of ITO are even more challenging than that of a metal. ITO isnot always conductive like a metal and some process settings which mayresult in a smooth coating for a metal may not result in a highlyconductive coating with ITO. Therefore, controlling the morphology inlight of other properties of the material is quite challenging. Ingeneral, for high temperature coatings on glass or other vitreoussubstrates, relatively smooth coatings may be obtained at high pressuresand relatively high oxygen settings as describe earlier in thisdocument. Variation in process parameters to smooth a coating can beapplied to other materials as well such as TiO2 or multi-layers such asTiO2 and ITO taught in transflective coating applications.

As noted above, the roughness generally increases with the thickness ofthe coatings. Often the process settings described above areinsufficient to result in coatings with an acceptable roughness level.This is the case where extremely low sheet resistance values are needed.In this scenario alternate means are needed to attain coatings withrelatively low surface roughness that simultaneously have low sheetresistance values.

In commonly assigned US Patent application publication number2006/0056003, the entire disclosure of which is incorporated herein byreference, an ion beam is introduced as a means to thin a coating in alocal area on a coated substrate. As discussed at length herein, an ionbeam may also be used to smooth (as depicted in FIGS. 33 a and 33 b) arough coating (as depicted in FIG. 37). An ion beam may be used eitheralone or in conjunction with other methods taught herein to reduce theroughness of a coating and thus increase the reflectivity. Ion beamsources vary in design and function. For the purpose of this discussion,any design capable of delivering fluxes of ions at the energy rangesdescribed herein are suitable.

An ion beam is a relatively collimated group of energetic positive ornegative ions. The energy of the ions is a function of the operatingpotential of the ion beam. The current, or flux of ions, is a functionof the operating potential and the amount of gas fed through the beamand the back ground pressure in the chamber. Sufficient energy for theions is desirable to etch, mill away and/or smooth the coating material.An example of a related phenomenon is that of billiards. Consider theincoming ion as the cue ball and the coating as the rack of balls at thestart of the game. If the cue ball is shot at the rack with very lowenergy then the rack does not break apart. Conversely, if the cue ballis shot with high energy then the rack can be broken apart quiteviolently.

FIG. 34 depicts sputtering yield as a function of argon ion energy forvarious materials. There is a threshold energy whereby no or minimalsputtering occurs. As the energy is increased the sputtering yieldincreases. The ionized atom may also affect the sputtering rate. Thepreferred mass of sputtering ion to have the maximum sputtering yieldwill vary with the energy of the sputtering ion and the mass of theatoms to be sputtered. FIG. 35 depicts sputtering yield as a function ofsputtering ion and sputtered atom mass at 500 eV ion energy. The datadepicted in FIG. 35 was generated using a computer simulation programcalled “Stopping and Range of Ions in Matter (SRIM)”. As depicted thereis a range of optimal sputter gas ion masses which will produceacceptable sputtering yields for a given target atomic mass. In general,as the beam energy is increased the optimal mass of ions increases tomaximize the sputter yield. To some extent, the preferred ion will bedependent on the mass of the sputtering atom. For optimal energy andmomentum, transfer of the atoms should be of relatively comparable mass.FIG. 34 depicts that the threshold energy is dependent on the sputteredmaterial. Some materials take more energy to release than others. Thegraph of FIG. 34 also depicts that at relatively high energy of the ionthe sputtering yields tend to plateau. At these relatively highenergies, the process starts to move into the region of ion implantationrather than ion sputtering. For efficient sputtering or etching, the ionenergy should be above 100 electron volts, preferably above 500 electronvolts and most preferably above 1000 electron volts.

The smoothing effect is illustrated with reference to FIGS. 36 and 37.In FIG. 36 an ion is impinging on a smooth surface. When the ion hitsthe surface, energy is transferred both parallel and perpendicular tothe surface. Some of the energy which is transferred parallel to thesurface may result in a component perpendicular and away from thesurface which results in an ejected atom. In FIG. 37 the same ionimpinges on a rough surface. As can be appreciated, it is much morelikely that an ion is ejected from the coating. The majority of theenergy which is directed perpendicular to the surface may result inejection of an atom; there is more surface area and are more directionswhich can release an atom. As the ion milling process continues, thecoating becomes more and more smooth. In these and other examples theion beam is consisting of a single atom. In practice clusters ofions/atoms may be employed in lieu of single ions. Known methods toproduce clusters may be employed in this situation also.

In a similar fashion, an ion beam impinging on the surface at an anglemay have a substantially higher sputtering efficiency and smoothingeffect. In this case the angled ion beam would have a high probabilityof ejecting material laterally to the coating surface.

As noted below the reflectance, transmittance, absorption and sheetresistance properties of a particular transflective coating were limitedby roughness in the layers. One relevant coating is Glass/ITO/Si/Ruherein referred to as “Option 4”. The ITO is optimally a ¾ or 5/4 wavecoating, 2100 or 3600 angstroms, respectively. The Si layer is about 220angstroms and the Ruthenium layer is about 70 angstroms. Also asdiscussed below different variants of this stack are possible. Thereflectance and transmittance of this stack is very dependent on thesurface and interface roughness. When multi-layer stacks such as option4 are considered that consist of dielectric, semiconducting layers,transparent conduction oxides and metals then the interface roughnessmust be considered as well as the roughness of the surface.

Table 15 depicts the effect of ion milling the surface of ITO—one of thelower layers used in Option 4 stacks. The data was determined by usingellipsometry to characterize the coatings. Table 15 also depicts theinitial properties of the ITO coating. The initial roughness for the ¾and 5/4 wave coatings are 7.4 and 11.5 nm, respectively. These valuesare relatively high. The samples were ion milled with a single beam (38cm long beam) running at 270 mA current and 3000 volts with argon feedat 20 sccm and the operating pressure in the chamber was 2.5 mT. The ionbeam is a closed drift Hall-effect anode layer type design. The linespeed for the 2B (two beam equivalent at 30 ipm) case was 15 ipm and theline speed for the 4B (four beam equivalent at 30 ipm) was 7.5 ipm. Thebeam was oriented perpendicular to the surface of the coated glass. Theion beam removed about 17 nm/beam equivalent at 30 ipm for the ¾ waveITO and about 11.1 nm/beam equivalent at 30 ipm. The surface roughnessdrops dramatically in both cases with the ¾ wave ITO getting nearlyperfectly smooth. The 5/4 wave ITO did not get as smooth, however,because it started from a much more rough initial state it may require aslower line speed or additional beams to attain the minimal roughnessvalues.

TABLE 15 Ion milled ITO properties Ion Milling Data (Ohms/sq) (MicroThickness (nm) Average ohm cm) Rough- nm/Beam Sheet Bulk Bulk ness TotalRemoved Resistance Resistance 3/4 wave 233.0 7.4 240.4 5.9 141.0 ITO 3/4wave 203.0 1.4 204.4 18.0 6.4 130.3 ITO 2 beam 3/4 wave 177.2 0.2 177.415.8 6.8 121.0 ITO 4 beam 5/4 wave 369.0 11.5 380.5 4.0 150.3 ITO 5/4wave 351.0 7.1 358.1 11.2 4.2 149.5 ITO 2 beam 5/4 wave 331.1 4.9 336.011.1 4.4 147.8 ITO 4 beam

The key demonstration is the substantial increase in reflectance withthe ion milling process. In Table 16a the ITO coatings described inTable 15 are overcoated with approximately 22 nm of Si and 7 nm of Ru.The transmittance generally decreases with ion milling due to the higherreflectance of these coatings. More importantly the absorption of theion milled ITO samples is appreciably lower. This results in higherlight output of associated light sources through the coating at the samereflectivity level. The differences are much more significant when allof these coatings are normalized to the same reflectance level. In orderto attain the same reflectance levels for the non-ion milled parts thethickness of the Ruthenium layer is substantially increased. This, inturn, further reduces the transmittance and increases the absorptionwhich is undesirable in some applications.

These coated lites, as tabulated in Table 16a, were incorporated intoelectro-optic mirror elements, as tabulated in Table 16b, to evaluatethe optics in an actual EC element. A number of 2″×5″ cells were madeand the transmittance and reflectance (specular and non-specular) weremeasured. The increase in reflectance of the assembled elementscorrelates with the results observed in the singles data. Thetransmitted color is very amber biased even though the reflected coloris quite neutral. This implies that this design, due to its uniquematerials of construction, transmits more red light than blue light.This can be of particular advantage when a red display, for example ispositioned behind the mirror element.

Table 16b also depicts the specular excluded reflectance (Spec Ex) datafor the sample elements. Ion milling smoothes the surface whichsubstantially reduces the scattered light. The resultant image is muchclearer and crisp due to the lower amount of scattered light.

Many automotive companies have specifications dictating that thereflectance must be above 55% for an outside mirror application. Thenon-ion milled samples did not meet this specification with the initialamount of roughness on the ITO. The ion milled samples, even the 5/4wave ITO parts, meet the specification. The switching speed of a mirrorelement, particularly the darkening speed, is dependent on the sheetresistance of the coatings. By enabling the use of a 5/4 wave ITO orthicker, the ion beam milling allows for faster switching times whilesimultaneously meeting the reflectance requirements. Also, some of the ¾wave elements have reflectance values that significantly exceed theminimum requirement. These coatings may be adjusted to have highertransmittance values by decreasing the thickness of the Ruthenium orother high reflectance metal used as the top layer when overall designrequirements benefit from this change. Without the ion beam smoothingmethod the useful range of reflectance and transmittance options wouldbe limited.

TABLE 16a Option 4 - Single Lite of Glass Results ReflectanceTransmittance Absorption Trial Y a* b* Y a* b* Y 3/4 wave ITO @ 3 mTPressure 66.3 0.6 0.8 9.9 2.3 19.6 23.9 3/4 wave ITO @ 3 mT Pressure and69.3 1.0 1.1 8.4 1.4 19.2 22.3 2 beam equivalent 3/4 wave ITO @ 3 mTPressure and 70.8 0.7 2.2 8.1 1.0 17.1 21.2 4 beam equivalent 3/4 waveITO @ 1.7 mT Pressure 67.7 0.6 1.2 8.7 2.8 20.1 23.7 3/4 wave ITO @ 1.7mT Pressure 70.0 1.1 1.4 7.7 1.9 19.6 22.3 and 2 beam equivalent 3/4wave ITO @ 1.7 mT Pressure 71.1 0.9 2.3 7.5 1.4 17.3 21.3 and 4 beamequivalent 5/4 wave ITO @ 3 mT Pressure 62.9 −1.3 2.0 10.5 4.9 16.0 26.65/4 wave ITO @ 3 mT Pressure and 65.7 1.0 1.5 8.9 1.5 17.9 25.4 2 beamequivalent 5/4 wave ITO @ 3 mT Pressure and 68.4 0.8 1.5 8.1 0.5 17.923.4 4 beam equivalent 5/4 wave ITO @ 1.7 mT Pressure 64.2 −1.2 2.4 9.45.2 16.6 26.5 5/4 wave ITO @ 1.7 mT Pressure 66.4 1.0 1.9 8.2 1.9 18.325.5 and 2 beam equivalent 5/4 wave ITO @ 1.7 mT Pressure 69.2 1.1 1.87.2 1.0 18.4 23.5 and 4 beam equivalent

TABLE 16b Cell data comparing ion milled parts properties Reflec- SampleID tance a* b* Transmittance a* b* Spec Ex 3/4 wave 54.2 −1.5 2.3 11.52.9 21.7 0.7 3/4 wave 2B 57.6 −0.2 3.1 10.4 0.9 21.6 0.2 3/4 wave 4B59.3 −0.7 4.4 10.0 1.0 19.1 0.3 3/4 wave 4B 58.5 −0.4 3.6 10.3 0.7 20.50.3 5/4 wave 50.1 −2.0 4.0 10.8 3.9 18.2 1.1 5/4 wave 2B 52.9 −0.6 3.611.0 2.1 19.8 0.8 5/4 wave 2B 52.1 −0.6 3.6 11.5 2.0 19.7 0.8 5/4 wave4B 55.6 −0.3 3.9 10.0 0.1 20.4 0.5 5/4 wave 4B 55.3 0.0 3.2 10.2 0.620.8 0.6

In another application, use of ion milling to smooth an ITO for anon-transflective application was performed. In this case, the coatingis Glass/ITO/Cr/Ru. The chrome and ruthenium are masked internal to theepoxy seal and the ITO is used to transfer electric current from theelectrodes to the EC element interior. The ITO has some degree ofroughness which is reduced by treatment with an ion beam. FIG. 38 showsdecreased roughness with inverse line speed at fixed beam current. Inanother example the line speed for the glass through the coater was 30inches per minute (ipm). A single ion beam was used and the current wasadjusted to vary the ion milling rate. FIG. 39 depicts the increase inreflectance versus beam current. A reflectance increase of 0.5% isattained with even this modest ion milling condition. In these examplesthe ITO coating maintained its initial roughness to potentiallyfacilitate increased adhesion of the ITO to the epoxy in the area of theseal while milling the ITO in the viewing area to attain improvedoptical properties.

In another application using the ion milling the color and reflectanceof a so-called chrome ring type coating was investigated. In thisapplication a multi-layer metal coating is applied on top of an ITOcoating that is on glass. The ITO coated glass was ion etched in a ringaround an element to thin the ITO coating in this location to improvethe color and reflectance of the chrome ring stack while enabling lowersheet resistance of the thicker ITO in the center of the part. FIG. 40depicts the reflectance of different conditions when viewed through theglass. The reflectance without ion milling is depicted as the bold line.The reflectance with several different line speeds are also depicted. Asthe speed is reduced, the residence time under the beam is increased andthe roughness is reduced. This results in an increase in reflectance.The reflectance appears to plateau, however, there was some arcing ofthe beam during these tests which may have affected the results. The keyresult is that with ion milling, even in the presence of arcing, thereflectance is increased. FIG. 38 depicts the change in ITO roughness inthese tests versus line speed under conditions without arcing.

Another set of tests in the same coater examined the color of the chromering with ion milling. The line speed was adjusted to alter the amountof ITO removed. The ITO started as a ½ wave and the goal was to reducethe thickness to approximately 80% of a ½ wave in other words fromapproximately 145 nm to approximately 115 nm. FIG. 41 depicts thereflected b* of the chrome ring with line speed adjustments. Thereflected b* is directly correlated with the thickness of the ITO asdescribed in the priority document incorporated herein by reference. Theb* for a ½ wave ITO coating is about 16. As the line speed is lowered,the amount of etched material is reduced. In at least one embodiment anideal match to the center viewing area a b* of about 2.5 is desired.Therefore, the line speed should be about 12.5 ipm. When faster linespeeds are required then more ion beams may be employed.

In another example where reduced sheet resistance values are desired theeffect of ion milling on reflectance and material usage wasinvestigated. As noted above, the roughness of a coating increases withthickness and the reflectance decreases with roughness. In this example,a coating with 1.5 ohms/sq with a layer structure ofGlass/Chrome/Ruthenium was desired. The chrome thickness was set toapproximately 2500 angstroms to provide the majority of the contributionto the sheet resistance. The Ruthenium was initially set to 400angstroms. In situations where the surfaces are perfectly smooth, themaximum reflectance will be attained with as little as 180 to 200angstroms of Ruthenium. A level of 400 angstroms was used to ensure thatthe Ruthenium was thick enough to compensate somewhat for the roughsurface of the chrome. The additional Ruthenium increases thereflectance but the cost also increases.

FIG. 42 depicts the reflectance versus inverse line speed for an ionbeam treatment of a chrome layer prior to the application of theRuthenium layer. The beam current was set to about 250 mA. At a linespeed of about 4″/minute the coating attains its maximum reflectance ofalmost 70.5%. Further reductions in the line speed did not result inadditional increases in reflectance. If faster line speeds are desiredthen additional beams may be employed.

FIG. 43 depicts how reducing the amount of Ruthenium may be used in thecoating due to the smoothing effect of the ion beam. The line speed wasat about 2.1 ipm and the beam current was comparable to the results inFIG. 42. As little as 160 angstroms of Ruthenium may be used to net themaximum reflectivity. This results in substantial cost savings relativeto the baseline case where extra Ruthenium was used to compensate forthe roughness of the initial layers. Additionally, a 1.5 ohm/sq coatingof chrome and ruthenium with relatively high reflectance may not haveeven been practical without ion beam smoothing.

Typically roughness of a coating produced without any special efforts tomake a smooth coating will vary between approximately 10 and 20% of thetotal thickness of the coating. Table 17 depicts the thickness ofchrome/ruthenium stacks needed to attain various sheet resistancevalues. The bulk resistance of the chrome layer is varied to demonstratehow the thickness of the chrome layer will vary to attain differentsheet resistance values as the bulk resistance changes. This may be usedas an example of variations in chrome bulk resistance properties or onecould consider this as a means to demonstrate what happens whenmaterials with different or varying bulk resistance values aresubstituted for chrome.

The range of roughness is calculated in Table 17 as 10 and 20% of thebulk thickness. The ruthenium is set at 200 angstroms which is justslightly above the thickness necessary to attain maximum reflectance forthat material in an ideal application. If the chrome layer is smooth orhas been smoothed by an ion beam then this thickness demonstrates theoptimal reflectance case. Table 17 depicts the results of calculationswhere the thickness of the ruthenium is compared to the total thickness.The contribution of the roughness is considered to be the average of the10 and 20% cases. The percentage of the stack that is ruthenium varieswith the target sheet resistance of the stack and with the bulkresistance of the chrome or base layer. It is desirable that theruthenium or other high reflectance metal to be less than 50% of thetotal thickness if the sheet resistance is greater than or equal to 6ohm/sq. If the sheet resistance of the stack is approximately 2 ohms/sqthen the ruthenium thickness should be less than about 25% of the totalthickness. The thickness percentage of the high reflectance layer willalso vary with the bulk reflectance of this metal and the reflectancetarget. The appropriate high reflectance percentage of total thicknessis a function of the desired reflectance of the stack, the desired sheetresistance of the stack and the bulk resistance of the differentmaterials being used to construct the stack. The percentage of the highreflectance material should be less than 50% of the total thickness,preferable less than 25%, more preferably less than 15%, even morepreferably less than 10% and most preferably less than 7.5% of the totalthickness. In this example chrome and ruthenium are used to demonstratethe benefits of one embodiment of the present invention. Other metalscan be substituted for the chrome layer as a means to provide themajority of the sheet resistance. The so-called high reflectance metalis defined as a metal that is of higher reflectance relative to thelayer that is contributing to the majority of the sheet resistance. Inthis example we discuss the role of the top most layer as having ahigher reflectance relative to the electrical conduction layer. In otherembodiments the electrical conduction layer or layers may have anunacceptable color or hue. The reflectance intensity may be acceptablebut the reflected color may be considered objectionable. In thisembodiment the top most, high reflectance layer, may in fact functionnot to increase the reflectance but rather to provide an acceptablecolor. In one example the electrical conduction layer may be highlycolored and a neutral reflected color is preferred. In this case the socalled high reflectance layer would act to make the color more neutral.

In another embodiment, the electrical conduction layer may have aneutral reflected color and a highly colored reflectance is preferred.Here the top, high reflectance metal may be selected to provide anon-neutral appearance. In yet another embodiment, a multi-layer stackmay be applied over the electrical conduction layer such that the stackattains low sheet resistance while having the flexibility to adjustcolor via adjustments to the multi-layer stack placed above theelectrical conduction layer. In this example, the multi-layer stackcould consist of metals, dielectric layers, and/or semi-conductorlayers. The selection of the materials comprising the stack, theirthicknesses, orientation relative to the electrical conduction layer andneighboring medium will be determined by the design criteria of a givenapplication.

TABLE 17 Sheet Resistance Analysis Minimum Maximum Bulk Sheet Bulk SheetTotal Chrome Chrome Chrome Resistance Resistance Ruthenium ResistanceResistance Sheet Thickness Roughness Roughness Chrome Chrome ThicknessRuthenium Ruthenium Resistance Ruthenium % 496 50 99 57 10.00 200 30 156.00 26.0% 909 91 182 57 5.45 200 30 15 4.00 16.1% 2148 215 430 57 2.31200 30 15 2.00 7.5% 4622 462 924 57 1.07 200 30 15 1.00 3.6% 9581 9581916 57 0.52 200 30 15 0.50 1.8% 261 26 52 30 10.00 200 30 15 6.00 40.0%478 48 96 30 5.46 200 30 15 4.00 26.7% 1130 113 226 30 2.31 200 30 152.00 13.3% 2433 243 487 30 1.07 200 30 15 1.00 6.7% 5040 504 1008 300.52 200 30 15 0.50 3.3% 130 13 26 15 10.00 200 30 15 6.00 57.1% 239 2448 15 5.45 200 30 15 4.00 42.1% 565 57 113 15 2.31 200 30 15 2.00 23.5%1217 122 243 15 1.07 200 30 15 1.00 12.5% 2522 252 504 15 0.52 200 30 150.50 6.5%

As the sheet resistance is lowered for various applications thethickness must be increased and thus the surface roughness is increasedand the reflectance is decreased. The reflectance of the coating thenwill drop to a low value relative to the Theoretical Maximum value. Thelower the sheet resistance value that is targeted then the lower thepercentage of the Theoretical Maximum reflectance value that isattained. For a coating with a sheet resistance of approximately 6 ohmsper square or less the techniques described herein will allow one toattain a reflectance greater than 90% of the Theoretical Maximum andpreferably greater than about 95% of the Theoretical Maximum. For acoating with a sheet resistance of approximately 3 ohms per square orless the techniques described herein will allow one to attain areflectance greater than 80% of the Theoretical Maximum and preferablygreater than about 85% of the Theoretical Maximum, more preferablygreater than about 90% of the Theoretical Maximum, and most preferablygreater than about 95% of the Theoretical Maximum. For a coating with asheet resistance of approximately 1.5 ohms per square or less thetechniques described herein will allow one to attain a reflectancegreater than 75% of the Theoretical Maximum and preferably greater thanabout 85% of the Theoretical Maximum, more preferably greater than about90% of the Theoretical Maximum, and most preferably greater than about95% of the Theoretical Maximum. For a coating with a sheet resistance ofapproximately 0.5 ohms per square or less the techniques describedherein will allow one to attain a reflectance greater than 70% of theTheoretical Maximum and preferably greater than about 80% of theTheoretical Maximum, more preferably greater than about 90% of theTheoretical Maximum, and most preferably greater than about 95% of theTheoretical Maximum.

In commonly assigned US Patent Application Publication number2006/0056003, which is incorporated herein in its entirety by reference,various metal stacks are discussed for a “chrome ring” mirror element. Athin chrome adhesion layer is deposited onto ITO and a layer of a metalwith a higher inherent reflectivity is deposited onto the chrome layer.Various higher reflectance metals were discussed. A second layer ofchrome is described that does not contribute to the appearance when thecoating is viewed from the glass side, however, is applied to minimizethe transmittance of visible and UV light. The reduction of visiblelight is to hide the seal material while the UV light is reduced toprotect the seal material during exposure to sunlight. Chrome wascontemplated in this example as a low cost means to reduce thetransmittance of the light, whether it be UV and/or visible. Other lowcost metals may provide the same function provided they have goodadhesion to the seal and to the higher reflectance metal.

The thickness of the high reflectance metal may also be simply increasedto also reduce the light transmittance but the high reflectance metalsare often relatively expensive and the sole use of these materials wouldresult in a higher price of the coating.

The following structure is discussed in reference to FIG. 64. Generally,a layer 6410 deposited on a glass substrate 6412 may be an ITO or anytransparent conducting oxide or other transparent electrode. Thetransparent conducting oxide or transparent electrode may consist of asingle layer or multilayer. The layers in a multilayer may be selectedto modify the reflected color or appearance such that the “ring” has theappropriate optical properties. One such multilayer may include the useof color suppression layers placed between the glass substrate and thetransparent conducting oxide. The use of this layer leads to moreselections of color for the ring as the ITO layer thickness is adjusted.

An “adhesion layer” 6414 may be Chromuim, Ni, NiCr of variouscompositions, Ti, Si, or silicon alloys, or other suitable adhesionenhancement layer. A layer 6416 includes a high reflectance metal thatis selected from metals and alloys having bulk reflectance values thatare higher than that of Chromium. Exemplary metals include aluminum,ruthenium, rhodium, iridium, palladium, platinum, cadmium, copper,cobalt, silver, gold and alloys of these materials. In addition toalloys, mixtures of these metals with each other or with other metalsmay be employed. Multi-layers may also be used in place of the singlelayer shown in the schematic for the high reflectance metal. Similarly,a layer 6418 is a UV-blocking layer that may consist of a singlematerial, alloy, multi-layer or other combination which results in theappropriate reduction of transmittance of UV light.

The adhesion of materials, layer or coatings may also be improved by useof the ion beam treatment described herein. For example, ion beamtreatment of an ITO surface was performed using argon and then a mixtureof argon and oxygen. These tests were compared to non-ion milledsurfaces. The samples were attached to a test piece of glass by an epoxymaterial to form a sealed cavity. A hole was drilled in the top lite ofglass and the cavity is pressurized to determine the pressure valuenecessary for the cavity to fail. Failure mode may include cohesivefailure within the epoxy, adhesion of the epoxy to the coatings, factureof the glass or the coating may de-adhere from the substrate or theremay be intra-coating adhesion failures.

The surface of the layer 6410 was either ion beam treated with argon,argon/oxygen mixture or had no treatment. The surface was then coatedwith a thin layer of chrome about 50 angstroms thick followed by aruthenium layer approximately 500 angstroms thick (so called Beta Ring).The coated glass was bonded to another piece of glass with an epoxytypically used in EC elements and the epoxy was then cured. Table 18depicts the pressure values at failure and the amount of metal lift fromthe ITO coating. The control parts have trace amounts of metal lift. Theargon beamed parts had substantial lift of metals but the pressures atfailure were essentially the same. The use of oxygen had again similarpressure values at failure but the lift of metals from the ITO waseliminated. The oxygen improves the adhesion of chrome to the ITO. Theion beam will preferentially sputter oxygen which is a component whichhelps the adhesion of chrome. The argon only case results in aminimization of critical oxygen and a weaker bond. Adding oxygen intothe beam, it is believed, “heals” the ITO surface thus strengthening thebond and minimizing the metal lift. The pressure values at failure donot show a correlation because the glass is fracturing during the test.This fracturing determines the pressure value at failure and thusdominates the test. In this example, the oxygen is necessary but theremay be situations where other gases may be preferable or argon alone maybe the better choice.

In another example, where the layer 6416 is not present and where theRuthenium layer 6416 is deposited directly onto the surface of the ITOlayer 6410, a dramatic change in the pressure values at failure and achange in failure mode was observed. When the ion beam treatment is notused the pressure values at failure are quite low, approximately 6-7psi, and the coating lift was the failure mode; the glass does notfracture. When the ITO surface is treated with an oxygen containing beamand ruthenium is then deposited on the surface the pressure values atfailure increase by over a factor of 2 and the glass fracture is thedominant failure mode. The coating still lifts from the ITO layer butthe adhesion strength is dramatically increased.

TABLE 18 Pressure values at failure and amount of metal lift from ITOcoating. Blow Values (psi) Lift % A B C A B C 10.8 11.8 11.5 trace 45 010.4 12.2 9.9 trace 40 0 10.6 11.6 12.2 5 trace 0 12 9.4 9.9 5 30 0 99.7 10.2 5 20 0 12.4 11.4 9.3 0 40 0 11.2 9.4 9.7 0 40 0 10.4 11 9.5 060 0 9.7 11.6 11.1 5 20 0 11.8 8.9 11.5 0 40 0 9.7 10.4 9.5 5 20 0 11.59.4 11.8 trace  0 0 10.3 30 9.1 30 10.7 30 11.1 35 A—Beta Ring ControlsB—Beta Ring with Argon Ion Milling C—Beta Ring with Argon/Oxygen IonMilling

The very top layer 6420 in FIG. 64 is optional and may include anelectrical conduction stabilizing material, the thickness of which, insome application, is approximately 100 Angstroms. The role of this layeris to facilitate electrical conductivity and provide for a stableelectrical contact between the ring metals and the bus bar or silverpaste. The material may be selected from the platinum group metals suchas iridium, osmium, palladium, platinum, rhodium and ruthenium. Mixturesor alloys of these metals with each other or with other suitable metalsmay be used.

The thicknesses and selection of the materials in the layers arepreferably defined to provide the appropriate color and reflectanceintensity as taught in the referenced patent application. The thicknessof the layers should also be selected to attain the necessarytransmittance properties. The visible transmittance should be set sothat the epoxy seal is not visible when viewed. The visibletransmittance should be less than 5%, preferably less than 2.5%, evenmore preferably less than 1% and most preferably less than about 0.5%.The UV transmittance may or may not correlate exactly with the visibletransmittance. In the case of the UV transmittance the appearance of thering is not the issue but rather the protection of the seal is theprinciple concern. This of course presumes that the selected seal issensitive to UV light. The amount of allowable UV light is dependent onhow susceptible the seal is to the UV light. Ideally, the coating shouldbe designed such that the ring coating is opaque to UV light butunfortunately this level of UV transmittance may be cost prohibitive.Additionally, the adhesion of the layers may be compromised if the totalthickness becomes too large. The stresses which may be present in thelayers would result in a strain large enough to cause the layers todelaminate from the glass or other layers of the coating. For thisreason one needs to contemplate a finite amount of UV transmittance. TheUV transmittance should be less than about 1%, preferable less than0.5%, more preferably less than 0.1% and most preferably less than0.05%.

One feature/area that is gaining popularity is the use of the exteriormirror to display features such as turn signals, heater on/offindicators, door ajar warnings or warning to oncoming traffic that adoor may be about to open. The mirror or mirror housing is also beingused to house puddle or approach lighting.

The requirements are unique for an inside mirror when compared with amirror for outside the vehicle. In at least one embodiment the specularreflectance of an inside mirror is preferably 60% or higher andpreferably has ample transmittance in front of the display to pass anadequate amount of light through the associated mirror element.Furthermore, an inside mirror does not have to withstand the harshchemicals and environmental challenges encountered in an outside mirrorapplication. One challenge is to balance the need to meet automotivespecifications for a rearview mirror and the desire to incorporate anaesthetically pleasing information center. Providing high mirror elementlight transmittance is one means to compensate for limited light outputdisplay technologies. Often times high transmittance results incircuitry and other hardware behind the mirror element being visible. Anopacifier layer may be applied on the fourth surface of the mirrorelement to combat this problem.

A supplemental turn signal as depicted in FIG. 5 a is one example of adisplay feature desirable in an outside mirror assembly. One way toincorporate a signal feature behind an electrochromic mirror element isto laser ablate some of the reflective material from the element toallow light to pass through. A desire to offer alternative styling anddesigns is motivation for employing transflective mirror elementtechnologies. The transflective approaches of some embodiments of thepresent invention allow features in the mirror with a much more“stealthy” (covert) appearance. Stealthy allows light to pass throughthe transflective element while blocking the view of the source of thelight. Stealthy may also or alternatively mean that there is minimalcontrast between the display area and the main reflective area. In someinstances there is a desire to clearly indicate the display or featurewith a contrast in color or in reflectivity to give a framing effect sothat the viewer has a clear indication of where to look for the desiredinformation. Traditional materials utilized in outside mirrorapplications typically have low reflectivity, and or, high sheetresistance associated with achieving an appreciable transmittance level.

For example, ruthenium is often used in outside EC applications becauseof its relatively high reflectance and environmental durability. A 23 nmRu coating as the reflector in an EC element would have a reflectance ofapproximately 57.5% a level that would meet most commercial mirrorreflectance specifications. This coating would have a sheet resistanceof approximately 20 ohms/sq and the EC element would have atransmittance of approximately 2.5%. Neither the transmittance nor thesheet resistance is viable for practical applications. Otherenvironmentally durable metals may have slightly different reflectance,transmittance and sheet resistance values but none will have theproperties to meet the requirements in an EC application.

A lower reflectivity requirement for OEC elements enables use ofdifferent configurations of materials including silver, silver alloys,chrome, rhodium, ruthenium, rhenium, palladium, platinum, iridium,silicon, semiconductors, molybdenum, nickel, nickel-chrome, gold andalloy combinations for the associated reflective and, or, transflectivelayer(s) stacks with fewer difficulties in meeting the preferredreflectance, durability and electrochromic performance characteristics.Some of these materials have an advantage over silver or silver alloysin that silver and silver alloys are susceptible to damage in an outsidemirror environment. Use of harder metals is advantageous for durabilityof the mirror element in terms of manufacturing options and a morerobust final product. Reflective and, or, transflective stacks may alsobe created with dielectric materials which produce high enoughreflectance levels for use in an OEC element.

Ag based materials will generally gain approximately 1% transmittancefor every percent of reflectance reduction in the mid-visible range. Anadvantage associated with increased transmission is the ability toutilize lower cost, lower light output light sources, such as, displaysor LED's. The outside mirror has typically been used for indication typedisplays that generally use LED's that can be ordered with very highlight outputs. Novel designs are disclosed herein that enable the use ofAg based transflective coatings in inside and outside mirrorapplications. These novel designs preserve the unique optical propertiesand benefits derived from the Ag layer while simultaneously addressingthe limitations for using Ag based materials in outside applications.Different coating options may be considered when lower transmittance ispart of the design criteria using stacks that have and do not have an Agbased layer. One big advantage to a lower transmittance is thereduction, or elimination, of the need for an opacifier layer.

In many markets the size of the mirror is increasing to allow for morefield of view. The darkening time for larger mirrors is a challenge andis an important consideration in the design options. Larger mirrors,generally associated with outside mirrors, require increased or improvedconductivity to maintain an acceptable darkening and clearing speed. Theprevious limitations of a single thin metal coating as described aboveare solved by the innovative use of a Transparent Conductive Oxide (TCO)in the stack. The TCO provides a means for achieving good conductivitywhile maintaining a high level of transmittance. Several of thefollowing examples illustrate that satisfactory levels of transmittancefor outside mirrors can be achieved with relatively thick Indium TinOxide (ITO. ITO is one specific example of the broader TCO class ofmaterials. Other TCO materials include F:SnO2, Sb:SnO2, Doped ZnO, IZO,etc. The TCO layer is overcoated with a metal coating that may consistof a single metal or alloy or a multilayer metal coating. The use ofmultiple metal layers may be needed, for instance, to facilitateadhesion between different materials. In another embodiment asemiconductor layer may be added in addition or in lieu of the metallayers. The semiconductor layer provides some unique properties thatwill be discussed below. When the thickness of the ITO/TCO layer(s) isincreased to improve conductivity the effects of coating roughness needto be considered. The increased roughness can lead to lower reflectancewhich in turn requires increased metal thickness which can lowertransmittance. Increased roughness can also lead to unacceptable haze asdescribed elsewhere. The roughness issue can be solved by eithermodifying the deposition process for the ITO and/or implementing ionbeam smoothing after the ITO deposition and before the deposition ofsubsequent layers. Both methods were discussed above in detail. Inaddition, improved ITO materials discussed above may be employed in thisembodiment to lower the sheet resistance of the overall transflectivecoating.

The semiconductor layer may comprise Silicon or doped silicon. Smallamounts of an additional element or elements may be added to alter thephysical or optical properties of the Silicon to facilitate its use indifferent embodiments. The benefit of a semiconductor layer is that itenhances the reflectivity with less absorption compared to a metal.Another benefit of many semiconductor materials is that they have arelatively low band gap. This equates to an appreciable amount ofabsorption in the blue to green wavelengths of the visible spectrum. Thepreferential absorption of one or more bands of light lends the coatingto have relatively pure transmitted color. The high transmitted colorpurity equates to having certain portions of the visible or nearinfrared spectra with transmittance values greater than 1.5 times thetransmittance of the lower transmitting regions. More preferably thetransmittance in the high transmitting region will be greater than 2times the transmittance in the low transmitting region and mostpreferably greater than 4 times the transmittance in the lowtransmitting region. Alternately, the transmitted color of thetransflective stack should have a C* value, that is equal to[sqrt(a*²+b*²)], to be greater than about 8, preferably greater thanabout 12 and most preferably greater than about 16. Other semiconductormaterials that result in transflective coatings with relatively highpurity transmitted color include SiGe, InSb, InP, InGa, InAlAs, InAl,InGaAs, HgTe, Ge, GaSb, AlSb, GaAs and AlGaAs. Other semiconductormaterials that would be viable would be those that have a band gapenergy at or below about 3.5 eV. In an application where stealthycharacteristics are desired and a red signal is used then a materialsuch as Ge or an SiGe mixture may be preferred. Ge has a smaller bandgap compared to Si and this results in a greater wavelength range thathave relatively low transmittance levels. This can be preferred becausethe lower transmittance at wavelengths different from the display aremore effective at hiding any features behind the mirror. If a uniformtransmittance is needed then it would be advantageous to select asemiconductor material that has a relatively high band gap.

A display area may be stealthy in nature such that an observer may notperceive that the mirror has a display until the display it is activatedor back lit. Stealthyness is achieved when the reflectivity of thedisplay area is relatively similar to the remaining viewing area and thecolor or hue contrast is minimal. This feature is very advantageousbecause the display area does not reduce the viewing area of the mirroras discussed above.

A small amount of transmitted light can make features behind the mirrorvisible such as circuit boards, LED arrays, shrouds and heaterterminals. Use of a light blocking (opacifying) layer may be used toavoid this problem. An opaque layer is often applied on the fourthsurface of the mirror using a variety of materials such as paints, inks,plastics, foams, metals or metal foils. The challenge of applying thislayer is complicated in an outside mirror. Most outside mirrors have aconvex or aspheric shape which makes application of a film or coatingmore difficult.

An opacifying layer may be incorporated into the third surface stack ofthe element. The transflective area may be masked and an appropriatestack such as ruthenium, rhodium or other single or multi-layer stack(metals, metal/dielectrics and or dielectrics) which provide theappropriate reflectance and color (opaqueness) may be applied over theremaining surface. The stealthy appearance is achieved when desiredcolor and reflectance match or mismatches are maintained. In onepreferred embodiment the display area and the main viewing area of themirror element are virtually indistinguishable. In other embodiments onemay want the transflective area to have a different color with anaesthetically pleasing contrast.

Another option is to maintain high transmittance levels in one part ofthe visible spectrum with low overall transmittance to obtain a stealthyappearance. Use of a narrow spectral band pass filter may also beemployed to obtain the stealthy effect.

Inserting a relatively opaque layer (whether of the same material or onedifferent than those in adjacent layers) into an otherwise transflectivethird surface coating stack maybe be incorporated to help hideelectronics that are behind the mirror element in without, or inaddition to, use of a coating or tape or other opacifying material onthe rear surface of the element. Addition of this layer may affect thereflectance in the area where it is inserted. Reflectance in this areamight then be adjusted, through choice of materials and theirthicknesses, such that the difference between A display area and therelatively opaque areas of the mirror element are hardly noticeable,thereby preserving the unity of the appearance of the device.

It may also be advantageous to purposely offset the reflectivity and/orhue of the display area to give a visual cue as to where the displaywill be when it is active and give some indication that a displayfunction is included in the mirror even when the display is off. When aconductive material is used to add opacity the conductivity of therelatively opaque portion of the display is now greater and there is acorrespondingly smaller voltage drop across the majority of the viewingarea providing a faster coloring speed. Additional opacifying layer(s)may be such that the reflectivity from the back of that area issubstantially less than without the opacifying layer(s), thereby,lessening the effect of multiple reflections that may otherwise occurfrom stray light. One such device demonstrating the aforementionedprinciples includes a third surface coating stack of approximately 400angstroms T_(i)0₂ followed by 200 angstroms of ITO over substantiallyall of the entirety of the third surface followed by approximately 90angstroms of chrome except for an area roughly over the display followedby approximately 320 angstroms of 7% gold 93% silver alloy oversubstantially the entire third surface.

The opening for the display on this particular model of insideautomotive mirror is too small for measuring reflectance with somesphere based spectrophotometers, therefore, elements were made withdifferent portions of the stack over their entire viewing surface inorder to facilitate measurement of reflectance of the different portionsof the stack. Transmission and reflectance measurements were taken fromboth the front and back of the elements.

Tables 19 and 20 along with the graphs of FIGS. 44 and 45, respectively,depict the resulting measurements

TABLE 19 Measurements in an Element A illuminant 10 Degree ObserverReflectance values Y L* a* b* Comments 400A TiO2/200A ITO/90A 36.8 67.2−3.5 −1.7 Chrome Front 400A TiO2/200A ITO/90A 10.8 39.3 −4.5 −23.6Chrome Back 400A TiO2/200A ITO/90A 79.3 91.4 −1.9 2.9 as in the moreChrome/320A 7Au93Ag opaque area Front 400A TiO2/200A ITO/90A 24.9 57.0−3.4 −17.0 as in the more Chrome/320A 7Au93Ag opaque area Back 400ATiO2/200A ITO/ 74.7 89.3 −1.0 4.0 as in the 320A 7Au93Ag Front displayarea 400A TiO2/200A ITO/ 76.3 90.0 −0.2 2.3 as in the 320A 7Au93Ag Backdisplay area

TABLE 20 Measurements in an element A illuminant 10 Degree ObserverReflectance values Y L* a* b* Comments 400A TiO2/200A ITO/90A 24.5 56.61.4 5.2 Chrome Front 400A TiO2/200A ITO/90A 3.7 22.8 −0.1 −0.9 as in theChrome/320A more opaque 7Au93Ag Front area 400A TiO2/200A ITO/320A 13.543.5 −4.4 −4.9 as in the 7Au93Ag Front display area

It can be seen that for this particular example, the addition of chrometo the stack adds opacity and lowers reflectance from the back of theelement. If in order to achieve opacity the thickness of the silveralloy were increased in the non-display areas it would not yield thereduction in reflectance from the back of the element as seen in thisexample but would increase further the already relatively highreflectance seen from the back of the element if the chrome wereomitted. It can also be seen that the display area of this design whencompared to the area with the chrome layer included, has a difference inhue that is relatively small as is the difference in brightness, eventhough the transmission is sufficient in the display area to serve as atransflector.

It should also be noted in the preceding example that by increasing ordecreasing the thickness of the silver alloy layer in the transflectiveregion, a greater or lesser “blue bias” will be obtained, respectively,in the transmission characteristics of this display region. Using an RGBvideo display behind this region may benefit by adjusting the relativeintensity of the red, green and blue emitters in order to maintainbetter color rendering. For example, in the case of transmission thatwas greater for the blue region of the spectrum and lesser for the redregion it may be desirable to decrease the intensity of the blue emitterand increase the intensity of the red emitter. This type of adjustmentwould be appropriate in this and other transflective designs whether thespectral bias of the transmission is a gentle slope or one with moredistinct bands of transmission.

When the display is intended for use when the mirror element is dimmedintensity adjustments may be made to compensate for any spectral biasfrom the coatings and, of, the activated electrochromic medium. Theintensity adjustment, may be a function of the operating voltage of thedevice, and or, other feedback mechanism to match the relative RGBintensities appropriately for a given point in the color excursion ofthe electrochromic element. When dyes are used, such as those that mightbe used to create a “blue mirror” even when the electrochromic speciesare not active, the intensity of the emitters may be adjusted to haveimproved color rendering. As the mirror element decreases inreflectivity, any spectral bias of first and/or second surface coatingswill become more of a factor; the degree of compensation of theintensities of the different colors of the display may correspondinglybe adjusted. UV absorbers and other additives to the EC medium may alsoaffect the visible absorption of the element intensity adjustments maybe incorporated to improve color rendering of an associated display.

It may be advantageous to design a transflective coating for bothdisplays and signal or other indicator applications. When high output isnecessary for the signals or indicators, the transmittance spectra ofthe transflector may be biased to accentuate the transmittance in thisregion. An RGB display with equal intensities in the red, green and blueparts of the spectrum would have different intensities after passingthrough the transflective layer (and other components of the mirrorelement). This offset in intensities may then be correspondinglycompensated by adjusting the output of the individual RGB colors to getproper color rendering.

There may be situations where the reflectance match between the opaqueand display areas is more desirable than the example in Tables 19 and20. Additionally, there may be benefits for having the reflectance matchat a range of different reflectance values. In this manner, thetransmittance of the display area may be adjusted without compromisingthe reflectance match between the opaque viewing area and the displayareas. Another design objective is to have the color either match in theviewing and display areas or to be different in an aestheticallypleasing fashion. A color match may be beneficial when the leastperceptible difference between the two areas is desired. In othercircumstances it may be beneficial to have a reflectance match but acolor mismatch to help guide the viewer to where the display is located.

Other means may be employed to further reduce the reflectance in theopaque area when viewed from the reverse direction independent of thefirst surface reflectance. Another aspect of the invention relates tothe perception of the display area relative to the opaque or viewingarea. The viewer will see only reflected light in the viewing area whilein the display area the viewer will see a combination of reflected andtransmitted light. The addition of the transmitted light in this areamay make the display area noticeable even though the reflectance in bothareas is identical. Therefore, the reflectance in the display area maybe reduced to compensate for the added transmitted light.

It should be noted that in the previous example the reflectance matchbetween the opaque areas and the display areas is a function of thethickness of the layers. The thickness of the chrome and AgAu7x wereoptimized so that the reflectance match was relatively close while stillhaving a relatively low transmittance. The change in reflectance andtransmittance as a function of the chrome and AgAu7x thickness is shownin Table 21. The data in Table 21 is modeled data for an Electrochromicelement consisting of the identified stack, 0.14 microns of EC fluid,and a top plate with a ½ wave of ITO coating on the 2^(nd) surface. Thereflectance difference between the opaque and display areas are lowerwhen the chrome layer is relatively thin and/or when the AgAu7x layer isrelatively thick. This approach provides for a means to make a mirrorwith an opaque area and a display with a fairly good match in certaintransmittance and reflectance ranges.

TABLE 21 Optical properties of calculated stacks with and withoutopacifying chrome layers Transflective Examples 2 degree, D65 R CapReflectance Stack Y a* b* Transmittance Difference Glass/45 nm TiO2/18nm ITO/0 nm Cr/15 nm AgAu7x 48.4 −3.8 −0.4 42.1 Glass/45 nm TiO2/18 nmITO/0 nm Cr/20 nm AgAu7x 58.1 −3.6 1.1 31.6 Glass/45 nm TiO2/18 nm ITO/0nm Cr/25 nm AgAu7x 66.1 −3.4 2.1 22.9 Glass/45 nm TiO2/18 nm ITO/0 nmCr/30 nm AgAu7x 72.3 −3.4 2.7 16.3 Glass/45 nm TiO2/18 nm ITO/0 nm Cr/35nm AgAu7x 76.9 −3.3 2.9 11.3 Glass/45 nm TiO2/18 nm ITO/0 nm Cr/40 nmAgAu7x 80.2 −3.3 3.0 7.8 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/15 nmAgAu7x 64.0 −3.8 1.6 13.1 15.6 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/20 nmAgAu7x 70.3 −3.7 2.2 9.7 12.3 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/25 nmAgAu7x 75.3 −3.6 2.5 6.9 9.2 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/30 nmAgAu7x 79.0 −3.5 2.7 4.8 6.7 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/35 nmAgAu7x 81.7 −3.4 2.8 3.4 4.8 Glass/45 nm TiO2/18 nm ITO/10 nm Cr/40 nmAgAu7x 83.5 −3.3 2.8 2.3 3.3 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/15 nmAgAu7x 70.3 −3.3 2.1 4.9 21.9 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/20 nmAgAu7x 75.2 −3.3 2.5 3.5 17.2 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/25 nmAgAu7x 78.9 −3.3 2.6 2.5 12.8 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/30 nmAgAu7x 81.6 −3.2 2.7 1.7 9.3 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/35 nmAgAu7x 83.5 −3.2 2.7 1.2 6.6 Glass/45 nm TiO2/18 nm ITO/20 nm Cr/40 nmAgAu7x 84.8 −3.2 2.7 0.8 4.6 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/15 nmAgAu7x 72.1 −2.9 2.1 1.9 23.7 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/20 nmAgAu7x 76.6 −3.0 2.4 1.4 18.5 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/25 nmAgAu7x 79.9 −3.1 2.6 1.0 13.8 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/30 nmAgAu7x 82.3 −3.1 2.6 0.7 10.0 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/35 nmAgAu7x 84.0 −3.1 2.6 0.5 7.1 Glass/45 nm TiO2/18 nm ITO/30 nm Cr/40 nmAgAu7x 85.1 −3.2 2.6 0.3 4.9

A means is desirable to attain a reflectance match over a broad range ofdesired reflectance values while maintaining opacity in the viewing areaand higher transmittance in the display area. This is attained in atleast one embodiment by adding an additional layer to the stackdescribed in the example of Table 21. This preferred third surface stackis TiO2/ITO/AgAu7x/Cr/AgAu7x. By splitting the AgAu7x the ability toachieve a reflectance match over a broad intensity range and have theability to simultaneously control the transmittance of the stack in theopaque area is attained. The transmittance in the display area islimited to the values previously described for AgAu7x stacks.

The chrome layer is masked in the area of the display while the otherlayers may be present over substantially the entire surface or, at aminimum, in the area of the display. This example uses a TiO2/ITO netquarter wave bi-layer (the so-called GTR3 base layer) to neutralize thecolor of the transflective silver or silver alloy layer in the area ofthe display. Other transflective color neutralization layers may besubstituted in the display area and are within the scope of thisembodiment. The chrome layer which splits the AgAu7x layer has the novelproperty in this application of not only providing an opaque characterfor the stack but it also optically isolates the lower layers from thetop AgAu7x layer. FIG. 46 shows how the reflectance varies with thethickness of the chrome layer. As can be seen, at a thickness slightlygreater than 5 nm the thin chrome layer effectively isolates the bottomsilver gold alloy layer from contributing to the reflectance. Thisisolation results with such a thin layer of chrome which allows thechrome thickness to be tuned to attain a range of transmittance valueswhile not having any applicable effect on the overall reflectance of thestack.

One benefit of this approach extends to the display area. Since only athin chrome layer is needed to isolate the bottom AgAu7x layer fromcontributing to the reflectance the thickness of the bottom AgAu7x layermay be varied to attain other design goals. For example, the desire tohave the reflectance match in the opaque area and in the display area aspreviously expressed may be achieved. In the examples wherein atransflective mirror element has regions of relatively hightransmittance and low transmittance the term “opaque” is meant toindicate that the transmittance level is sufficiently low to hide theappearance of components behind the fourth surface without the additionof opacifying materials on the fourth surface. In certain embodiment thetransmittance should be less than 5%, preferably less than 2.5% and evenmore preferably less than 1% and most preferably less than 0.5%. Sincethe AgAu7x is isolated in the opaque area, the thickness may be adjustedas needed to attain the desired reflectance in the display area. TheAgAu7x top layer will have a higher reflectivity when it is depositedonto Cr versus TiO2/ITO (as present in the display area). The bottomAgAu7x thickness may be set such that the display area matches thereflectance of the opaque area. The reflectance value for the mirrorelement may be as low as the reflectance value of the chrome layer aloneup to the reflectance of a thick AgAu7x layer. The reflectance can betuned to any desired value over this range and the transmittance can beadjusted as well. A desirable reflectance match between the display areaand the viewing area is also attainable.

The silver containing layers may be other alloys or combinations ofalloys aside from 7% Au93% Ag. For example, it may be advantageous tohave a higher amount of gold in the alloy above the opacifying layer(s)than under the layer(s). This may be for reasons associated withobtaining a more durable interface between the opacifying layer and theupper silver bearing layer, color desires or durability of the uppersilver bearing layer during processing or when in contact with theelectrochromic medium. If the two silver bearing layers containdifferent levels of materials that easily diffuse through the silversuch as gold, platinum, palladium, copper, indium or the like, thetransflective area where the silver layers no longer have one or moreintervening opacifying layers will likely become after processing ortime, an alloy that is the weighted average of the upper and loweralloys. For example if silver-palladium alloy were used as the uppersilver bearing layer and silver-gold alloy for the lower layer, then thetransflective region would likely become a silver-gold-palladium ternaryalloy layer. Similarly if equal thicknesses of 7% gold in silver and 13%gold in silver were used as the two silver bearing layers, the resultinglayer in the transflective region would likely be a layer withessentially uniform distribution of gold at 10% in silver.

The opacifying layer may be separate layers combined in thetransflective region where one, or both or all layers might not containsilver. For example, silver alloy over silicon may be employed in thetransflective region, or ruthenium over silicon, among many possiblecombinations.

Flash overcoat layers of materials mentioned in U.S. Pat. No. 6,700,692which is hereby incorporated in its entirety by reference, as useful forflash layers, which include among other materials, indium tin oxide,other conductive oxides, platinum group metals and their alloys, nickel,molybdenum and their alloys, may also be incorporated into the abovedescribed designs. Depending on the thickness and optical properties ofthe materials chosen for the flash layer(s) adjustments may be needed tothe underlying stack to maintain a similar degree of match or mismatchbetween the relatively opaque region and the transflective region(s).

As noted above the transmittance attainable in the “opaque” area isdependent on both the silver based layer and the chrome or “opacifying”layer. The thicker the chrome layer the lower the transmittance at agiven reflectance level. The chrome layer can be thinned to a desiredlevel to approach the transmittance of the display area. It is oftendifficult to control the thickness of a very thin layer if highertransmittance levels are needed. Thicker layers may be used if the metalopacifying layer is partially oxidized. A thicker layer may be needed toattain the higher transmittance relative to a thin pure metal layer.FIG. 47 depicts the relationship between transmittance and reflectancefor the stacks from Table 21 above and the case of using a CrOx layer asthe opacifying layer. FIG. 47 depicts transmittance versus reflectancefor different opacifying layers and thicknesses. The symbols in thechart represent different thickness AgAu7x layers. The thicker layersare to the right and the thinner layers are to the left.

As can be seen, as the thickness of the AgAu7x layer is thinned thereflectance approaches the value of the chrome or opacifying layer. Thethickness of the opacifying layer will affect the low end reflectance ofthe mirror element. For instance, when the Cr layer is 10 nm thick thelow end reflectance is 41.7%, 20 nm it is 50.5% and 30 nm it is 52.7%.The low end reflectance approaches a constant value as the opacifyinglayer is increased in thickness however, for thin layers there will be adrop in reflectance when the layer gets too thin. This can be anadvantage or disadvantage depending on the design criteria for a givenapplication. The limitations between reflectance and transmittance for achrome layer can be overcome by replacing the chrome layer entirely witha different material or by adding additional layers.

With reference to U.S. Pat. No. 6,700,692 different metals,semiconductors, nitrides or oxides are taught above or below the Agcontaining layer. These layers and materials are selected to provideimprovements to the stack. A base layer below the reflector is taughtwhich may be a conductive metal, metal oxide, metal nitride or alloy.There may also be an intermediate layer or layers between the base layerand the reflective material. These metals and materials may be selectedsuch that there are no galvanic reactions between the layers and/or toimprove adhesion to the substrate and to the reflector or otherlayer(s). These layers may be deposited on the substrate or there may beadditional layers below the previously mentioned base layers thatprovide additional desirable characteristics. For example, a dielectricpair comprising TiO2 and ITO with an effective odd quarter wave opticalthickness may be present. The thickness of the TiO2 and ITO layers maybe adjusted as needed to meet specific conductivity and opticalrequirements.

When a metal layer is deposited under the silver comprising layer it maybe selected from the group consisting of chromium, stainless steel,silicon, titanium, nickel, molybdenum, and alloys ofchromium/molybdenum/nickel, nickel/chromium, molybdenum, andnickel-based alloys, Inconel, indium, palladium, osmium, tungsten,rhenium, iridium, molybdenum, rhodium, ruthenium, stainless steel,silicon, tantalum, titanium, copper, nickel, gold, platinum, and alloyswhose constituents are primarily those aforementioned materials, anyother platinum group metals, and mixtures thereof. In addition the layerunder the reflector layer may be an oxide or metal oxide layer such aschromium oxide and zinc oxide.

An optional metal layer over the silver comprising layer may be chosenfrom the group consisting of rhodium, ruthenium, palladium, platinum,nickel, tungsten, tantalum, stainless steel, gold, molybdenum or theiralloys.

The present disclosure contemplates opacifying layers in conjunctionwith transflective portions of the mirror or optical element. Thispresents new or additional design criteria be included which affect theselection of metals which act to reduce the transmittance in certainareas of the element or mirror. Table 22 below shows the reflectance andcolor of various suitable base or opacifying layer metals on a TiO2/ITOdielectric layer stack in an EC cell. The thickness of all of the metallayers is 30 nm. The color and reflectance will vary with the thicknessof the metal layers. Table 22 depicts the relative differences in colorand reflectivity of various suitable metal opacifying layers on the lowend reflectance when the opacifying metal is relatively thick and theAgAu7x or other Ag comprising top layer is absent. As is known in theart, alloys of these metals with each other or with other metals willhave differing optical properties. In some cases the alloys will behaveas do mixtures of the individual metals, however in other cases thealloys do not have reflective properties which are simply theinterpolation of the individual metals. The metals or alloys can beselected for their galvanic properties, reflectivity, color or otherproperties as needed.

In silver containing reflective layer stack's the reflectivity and colorwill vary when deposited onto these different metals or alloys. Table 23depicts metal containing stacks with 20 nm of AgAu7x on top. The colorand reflectance of the 20 nm Ag containing layer stack is altered by theproperties of the metal used as with the opacifying layer. Thetransmittance of the different stacks is also shown. As shown above forchrome, the transmittance, reflectance and color can be altered bychanging the thickness of the opacifying metal. It is clear from theseexamples that a desired color, transmittance and reflectivity may beattained by altering the properties of the opacifying metal layer orlayers.

TABLE 22 Reflectance and color of various metals in an EC cell on top ofa TiO2/ITO base layer system. Stack R Cap Y a* b* Glass/45 nm TiO2/18 nmITO/30 nm Mo/0 nm 45.9 −2.2 1.6 AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nmAu/0 nm 50.8 1.3 16.6 AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm NiCr 52.8−2.1 4.4 (80/20)/0 nm AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm Si/0 nm36.9 −0.8 −3.4 AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm Pd/0 nm 55.8 −2.24.0 AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm Os/0 nm 37.4 −0.9 −9.8AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm W/0 nm 39.3 −0.2 4.8 AgAu7xGlass/45 nm TiO2/18 nm ITO/30 nm Rh/0 nm 63.9 −1.3 2.2 AgAu7x Glass/45nm TiO2/18 nm ITO/30 nm Ru/0 nm 60.3 −2.3 1.1 AgAu7x Glass/45 nm TiO2/18nm ITO/30 nm Ir/0 nm 56.0 −2.9 3.7 AgAu7x Glass/45 nm TiO2/18 nm ITO/30nm Cu/0 nm 48.4 −2.1 7.4 AgAu7x Glass/45 nm TiO2/18 nm ITO/30 nm Pt/0 nm51.2 −1.8 5.4 AgAu7x

TABLE 23 Reflectance and color of various metals and AgAu7x in an ECcell on top of a TiO2/ITO base layer system. Stack R Cap Y a* b*Transmittance Glass/45 nm TiO2/18 nm ITO/30 nm Mo/20 nm AgAu7x 73.2 −2.83.8 2.1 Glass/45 nm TiO2/18 nm ITO/30 nm Au/20 nm AgAu7x 78.4 −3.0 8.46.3 Glass/45 nm TiO2/18 nm ITO/30 nm NiCr (80/20)/20 nm AgAu7x 77.3 −3.14.2 1.9 Glass/45 nm TiO2/18 nm ITO/30 nm Si/20 nm AgAu7x 62.7 −2.0 0.515.8 Glass/45 nm TiO2/18 nm ITO/30 nm Pd/20 nm AgAu7x 78.8 −3.0 3.9 2.1Glass/45 nm TiO2/18 nm ITO/30 nm Os/20 nm AgAu7x 66.6 −1.0 −0.5 7.3Glass/45 nm TiO2/18 nm ITO/30 nm W/20 nm AgAu7x 70.4 −2.5 6.1 3.8Glass/45 nm TiO2/18 nm ITO/30 nm Rh/20 nm AgAu7x 80.9 −2.6 2.9 0.9Glass/45 nm TiO2/18 nm ITO/30 nm Ru/20 nm AgAu7x 78.5 −3.0 2.6 0.4Glass/45 nm TiO2/18 nm ITO/30 nm Ir/20 nm AgAu7x 78.3 −3.2 3.8 1.4Glass/45 nm TiO2/18 nm ITO/30 nm Cu/20 nm AgAu7x 76.4 −3.2 5.5 3.1Glass/45 nm TiO2/18 nm ITO/30 nm Pt/20 nm AgAu7x 76.8 −3.0 4.7 2.2Glass/45 nm TiO2/18 nm ITO/30 nm Cr/20 nm AgAu7x 76.6 −3.0 2.4 1.4

The ability to color and reflectance tune in the viewing area may befurther augmented or enhanced by combining the metal opacifying layerswith dielectric layers additionally described in the U.S. Pat. No.6,700,692. The dielectric layers may modify both the color andreflectance, often without having a substantial effect on the absorptionin the stack.

In order to match the color and reflectance in the display area thepreviously described bi-layer base layer under the silver containingreflecting layer may be employed. Table 24 depicts how the reflectanceand color varies with changes to the ITO and TiO2 thickness for a fixedAgAu7x layer. As can be seen the thickness of the bi-layers not onlyaffects the reflectance, but, the color can also be tuned. These layersmay then be adjusted as needed to get both the desired reflectance andcolor. The adjustability of the color and reflectance may be furtherexpanded by adjusting the thickness of the AgAu7x, or silver containingreflecting layer. Additional color and reflectance changes may beobtained by adding additional dielectric or metal layers as part of thedisplay stack either above or below the silver containing layer or bychanging the refractive indices of the dielectric layers.

Table 24: Color and reflectance changes with variations in the TiO2 andITO thickness of the base layer in the display area for a fixed silvercontaining layer thickness.

TABLE 24 Reflectance TiO2 ITO AgAu7x (cell) a* b* 20 15 20 46.2 3 4.8 3015 20 50.1 0.6 −1.2 40 15 20 56.2 −2.2 −1.2 50 15 20 61.5 −3.7 1.5 20 2520 50.3 1 0.7 30 25 20 56 −1.8 −0.6 40 25 20 61.6 −3.4 1.4 50 25 20 65.4−4.2 4.7 20 35 20 55.1 −1.1 0.5 30 35 20 60.8 −3.1 1.7 40 35 20 65 −44.6 50 35 20 67.3 −4.7 8.8 20 45 20 59.3 −2.6 2.3 30 45 20 63.9 −3.9 4.940 45 20 66.7 −4.7 8.9 50 45 20 67.6 −5.5 14.4

For example, when the color in the viewing area is yellow, blue, greenor red biased by choice of metal under the silver reflecting layer ordue to the silver reflecting layer itself or by a combination of thelayers then a color and/or a reflectance match may be achieved byadjusting the layers in the display area. One benefit of this approachis that layers can be applied over substantially the entire surface,however because of the unique optical shielding properties of theopacifying layer or layers, these lower layers do not contribute to thereflectance and color in the viewing or opaque area but are fullyfunctional in the display area where the opacifying layer or layers aremasked. The present invention is not limited to having the layers whichfunction in the display area cover the entire part. This is particularlyapplicable to layers under the opacifying layer. These layers may bedeposited as necessary only in the general area of the display shouldthe manufacturing process warrants this approach.

In some situations it might be advantageous for the reflector and ortransflector to be bluish in reflected hue. It could also beadvantageous to combine an opaque bluish reflector region and a bluishtransflective region in the same element for a stealthy appearance.

It is known to make blue electrochromic elements that have a blue hue tothem even when there is no potential applied to them through the use ofdyes such as in U.S. Pat. No. 5,278,693 which is hereby incorporated byreference in its entirety. There are also practical methods using thirdsurface coating stacks to make such a device that meets the typicalrequirements of outside automotive electrochromic devices. Thesetechniques could also possibly be used in combination. Such a devicemust, at present, have a reflectance value above 35% in the UnitedStates and 40% in Europe. Preferably in at least one embodimentreflectance values above 50% or 55% are preferred. Whatever thirdsurface stack is utilized needs to be durable, both chemically andphysically and electrically in an electrochromic device.

One can obtain a bluish Electrochromic device by depositing a layer ofchrome on glass that is essentially opaque and then depositingapproximately 900 A of ITO over the top of that and afterwardscompleting the construction of an electrochromic device. A coating stackmade and used in such a fashion had color values shown in Table 25 and areflectance spectrum shown in FIG. 53. Table 25 and FIG. 53 show valueswhen the coating is on a single lite of glass and after incorporationinto an EC element.

There will be a substantial reflectance drop when the coating on glassmeasured in air is compared to the reflectance in the completed device.To compensate one might think that an opaque layer of silver or silveralloy could be used instead of or in addition to the chrome layer with asimilar top layer or layers. However the optics of silver are such thatit is more difficult to obtain a high reflectance bluish coating over asilver based material. This is partly due to the slightly yellowspectral bias of silver and also due to the fact that as there is littleone can do to interferentially boost the reflectivity of silver in anyportion of the spectrum to give it significant color since thereflectance is already so close to 100% over the visible spectrum.

If one however places a translucent layer of silver or silver alloybetween the chrome and ITO in the stack above, one can still boost thereflectivity a significant amount, maintain a bluish color and increasethe conductivity of the third surface reflector electrode.

With a translucent layer of silver present one could make a region thatis transflective by the addition of color neutralizing underlayer(s) and“splitting” the silver and masking an opening in the chrome, inaccordance with teachings contained in this document.

For example a reflective stack of approximately 40 nm of TiO2, 20 nm ofITO, 14 nm Silver, 50 nm Chrome, 10 nm Silver and 90 nm ITO models asbeing similar in hue and brightness to the same stack without the Chromelayer. Without the chrome layer the transmission of the stack iscalculated as being adequate for use as a display or light sensorregion. Therefore one could mask the chrome during the deposition ofthat layer and make an electrochromic element with similar bluish hueand brightness (i.e. stealthy) in both the opaque and transflectiveportions of the device.

One might also boost the reflectivity of the Chrome\ITO stack throughthe insertion of a low index layer between the chrome and the ITO or bymultiple alternating low and high index layers. However most low indexoxide and fluoride materials in sufficient layer thicknesses to have theappropriate optical effect will also be electrical insulators. Silveritself is however a low index material and this does explain in part itsbenefit when placed between the chrome and ITO.

TABLE 25 Illuminant A 10 degree observer Chrome with about 900 AngstromsITO as single and as the 3rd Surface reflector electrode Y L* a* b*Single 49.571 75.805 −13.526 −15.323 element 44.315 72.439 −7.339 −7.896

Another feature beneficial in the area of display windows andtransflective coatings is an anti-reflection feature from the reversedirection. Often displays put out a substantial amount of stray lightwhich bounces or scatters around the back of the mirror element andeventually make its way out in the area of the display. By having theelements have a relatively low reflectance from the reverse directionthis stray light can be reduced. Attaining lower reflectance withoutadditional layers on the fourth surface has the added benefit of reducedcost.

Cr/TiO2/ITO/AgAu7x/Cr/AgAu7x is provided in the opaque or viewing areawhile having TiO2/ITO/AgAu7x/AgAu7x in the display area. The firstchrome layer is thin, about 2 to 15 nm thick, preferable about 5-10 nmthick and is masked in the display area. The second chrome is alsomasked in the display area and its thickness is adjusted to get thedesired transmittance in the viewing area. The TiO2/ITO bi layer coversthe entire surface and is adjusted to get the anti-reflectance effectfrom the reverse direction in the viewing area while providing theproper color in the display area from the front of the part.

Table 26 depicts the reflectance from the reverse direction, or from thefourth surface. The first case is the reference case. This is the stackdescribed above for the opaque or viewing area of the mirror element. Ascan seen the reflectance from the back is quite high at about 61%. Inthe second case a thin chrome layer (˜5 nm) is added below thedielectric layers. The addition of this thin layer in the viewing areareduces the reflectance to approximately 6% at 10 fold decrease inintensity. In this manner the scattering of any stray light will bereduced. This reflectance value, and its color, may be adjusted by thethickness of the chrome layer and the dielectric layers. Approximately4% of the 6.2% reflectance arises from the uncoated fourth surface ofthe glass. If further reductions in reflectance are desired anadditional traditional anti-reflection layer may be added. Thereflectance value of 6.2% could be reduced to values below 2.5%.

TABLE 26 Reflectance from reverse direction (fourth surface) with andwithout anti-reflection layer in the view area. These are assembledelement values. Stack R Cap Y Glass/35 nm TiO2/18 nm ITO/14 nm 61.4AgAu7x/25 nm Cr/8.5 nm AgAu7x Glass/5Cr/35 nm TiO2/18 nm ITO/14 nm 6.2AgAu7x/25 nm Cr/8.5 nm AgAu7x

The amount of reflectance reduction and its absolute value are dependenton the properties of the first silver containing layer and thesubsequent chrome layer. As described above these layers are adjusted totune not only the transmittance but also the reflectance toward theviewer. As these layers are adjusted to meet varying design goals ortargets, the dielectric layers and/or the base chrome layer may beadjusted to achieve the optimal anti-reflection effects.

Other metals or absorbing layers other than chrome may be used as theanti-reflection layer. Materials such as tungsten, chrome, tantalum,zirconium, vanadium and other similar metals will also provide a broadanti-reflection property. Other metals may result in a higher, morecolored reflectance. Additionally, the chrome or other metal layer maybe doped with small amounts of oxygen or nitrogen to alter the opticalproperties of the metal to adjust the anti-reflection properties.

The usefulness of an alternating set of a layer of high and lowrefractive index or multiple sets of such layers to modify the opticalproperties of a surface or thin film stack has been mentioned elsewherein this document. Materials that are typically thought of as being lowrefractive index that are metal oxides, nitrides, oxynitrides, fluoridestend to be poor conductors. Typically, the greater the difference inindices of refraction between adjacent materials the greater the opticaleffect. This is why a material with an index of refraction of about 1.6or less is usually used as the low index material. However, beneficialeffects arise with materials of higher index, such as transparentconductive oxides, when the material to which the TCO is coupled hassufficiently higher index of refraction and results in a high-low indexpair. In particular, when titanium dioxide is used as a relatively highindex material coupled with indium tin oxide as a relatively low indexmaterial benefits are obtained optically and electrically. In particulartitanium dioxide is a relatively high index of refraction material thatis not a sufficiently good insulator at optical thicknesses to isolatemore conductive thin films placed above or below it such as ITO, anotherTCO or a metal or semimetal layer or layers. When T_(i)O₂ is applied asan optical thin film between layers that are much more conductive, suchas Indium Tin Oxide, the T_(i)O₂ will not insulate the ITO layers fromone another in an electrochromic element and the desired optical effectof a high-low-high stack is achieved. In other words, most of thecumulative conductivity benefits of the total thickness of ITO in thethin film is retained along with obtaining the optical benefits of thehigh and low index layers. The following examples will illustrate thebenefits of this principle in general and these materials in particular.All base layers were deposited and measured on soda lime glass (napproximately 1.5 in the visible spectrum).

Base layer A=half wave optical thickness ITO of approximately 145 nmphysical thickness and 23 ohms/square sheet resistance (produced underconditions less than ideal for conductivity). Base layersB=approximately 40 nm titanium dioxide under approximately 20 nm ITOwith sheet resistance between about 110 and 150 ohms/square. Base layersC=Base layer A+base layers B with a sheet resistance of approximately 16ohms/square (the lower than expected sheet resistance may be due to thefact that capping the ITO layer of A before vacuum break and cooling mayhave enhanced the conductivity compared with layer A alone). Base layersD=approximately 42.5 nm titanium dioxide, 42.5 nm ITO, 42.5 nm titaniumdioxide, 42.5 nm ITO with a sheet resistance of about 40 ohms/square.FIG. 54 a depicts the reflectance spectra of these base layers on glassin air (without additional coatings and prior to assembly intoelectrochromic elements).

samples from the same coating runs (note that there will be somevariation even within a run) as the samples of FIG. 54 a were given anadditional coating of approximately 25 nm of 6% Au 94% Ag (referred toas 6×) alloy and assembled into electrochromic elements in accordancewith principles outlined elsewhere in this document. Half wave opticalthickness ITO with approximately 12 ohms/square on glass was used as thesecond surface coating for these elements. Spectrophotometricmeasurements were then taken as depicted in FIGS. 54 b and 54 c. Theresults are tabulated in Table 27.

TABLE 27 Reflected Color Values Illum L* a* b* Y Illum L* a* b* YElement with 6x and base layer C D65 85.183 −5.628 7.707 66.366 A 85.076−3.044 6.241 66.156 Element with 6x and base layer B D65 85.921 −2.8953.187 67.83 A 85.815 −1.824 2.358 67.618 Element with 6x and base layerD D65 84.769 −7.573 −1.199 65.555 A 83.838 −6.109 −3.781 63.754 Elementwith 6x and base layer A D65 82.573 2.453 15.379 61.362 A 83.845 5.06416.813 63.768

As mentioned previously, it is often useful to mask the silver alloy sothat it is, for the most part, not deposited under the seal area As aconsequence, if that option is chosen the electrical contact for theelement is made to the underlayer (s) on the third surface. In such aninstance lower sheet resistance for the underlayers becomes moreimportant than if the silver or silver alloy is taken all the way to thepoint of electrical contact via buss bar or conductive epoxy or othermeans.

Resistance measurements on the base layers described were taken with afour point probe that can give misleading results as to the surfaceconductivity if the probes break through insulating layers. Thereforeelements were constructed with just the base layer(s) as the thirdsurface coatings and compared for coloring and clearing characteristics.The performance of the elements was consistent with sheet resistancemeasurements taken via the four point probes.

In one embodiment of the present invention a color and reflectivitymatch between the viewing area and the display area may be desired. Insome examples mentioned above there may be two different metal stacks inthe two areas and if the same metal is the top layer the thickness ofthe layer may be different or other metals may or may not be below thetop metal layer. As singles, before being laid up into EC elements, thereflectance of the two areas may be adjusted to be substantially thesame. After lay up, when the medium in contact with the metals changesfrom air to that of the EC fluid the reflectivity may be different inthe two areas. This is because each stack interacts with the newincident medium in different ways.

For example, Ruthenium as the top layer in one design (Glass/TiO2 45nm/ITO 18 nm/Ru 14 nm) and AgAu7x in another (Glass/TiO2 45 nm/ITO 18nm/AgAu7x 19 nm) both are adjusted to have a reflectance as single of70.3% then when assembled into an element the Ru side will drop to 56.6%reflectance while the AgAu7x side will drop to 58.3%.

Another example TiO2 40 nm/ITO 18 nm/Cr 25 nm/AgAu7x 9 nm has areflectance of 77.5% as a single and 65.5% when assembled in an elementwhile TiO2 40 nm/ITO 18 nm/AgAu7x 23.4 nm has a reflectance of 77.5% asa single and 66% when assembled in an element. The difference in thiscase is not as dramatic as the earlier example, however it shows thateven buried layers can influence the reflectance drop going from asingle to an element. This is to illustrate that when reflectancematches are desired in an element a reflectance mismatch may be neededfor the coatings as singles.

The methods described above to attain good reflectance and color matchesin the two areas of the mirror presume that the appearance in the twoareas is due virtually entirely by the reflectance. However, the viewerperceives not only the reflectance but, in the display area, also thetransmitted light. In the viewing or opaque area the viewer onlyperceives the reflectance since the transmittance is relatively low. Theamount of transmitted light is a function of the transmittance in thedisplay area and the reflectance of components behind or in contact withthe fourth surface of the mirror. The amount of light perceived by theviewer increases as the transmittance of the coating in the display areaincreases. Similarly, as the reflectance of the components behind themirror increases the light perceived by the viewer also increases. Thismay add a substantial amount of light and the viewer would perceive thisas the display area being brighter than the viewing area. This mayresult in the display area appearing brighter even if the two areas haveidentical reflectance. This effect may be mitigated by producing anelement with components having low reflectance and/or by having thetransmittance in the viewing area set to a relatively low level. If theoutput brightness of the display is relatively limited, or low, thenreducing the transmittance can substantially dim the display.

For yet another example, an EC element consisting of 40 nm TiO2/18 nmITO/EC fluid/140 nm ITO/Glass having a reflectance of 8.1%. a 5 nmRuthenium layer is deposited on the fourth surface to simulate a displaybehind the mirror (i.e. 5 nm Ru/Glass/40 nm TiO2/18 nm ITO/ECfluid/ITO/Glass) the reflectance rises to 22.4%. An EC elementconsisting of Glass/40 nm TiO2/18 nm ITO/22 nm AgAu7x/EC fluid/ITO/Glasshas a reflectance of 61.7%. The stack with the 5 nm of Ruthenium has areflectance of 63.5%—approximately a 2% increase in reflectance. Thisamount of reflectance is quite perceptible by the viewer. As noted abovethe actual reflectance increase will be dependent on the reflectance ofthe components behind the mirror and the transmittance of the ECelement.

In order to reduce the perceived brightness differences in the two areasthe relative reflectance may be adjusted in the two areas to compensatefor the transmitted light component. Therefore, to achieve a net 2percent brighter area in the display section of the mirror eitherpreferentially increase the reflectance in the viewing area or decreasethe reflectance in the display area. The amount of adjustment isdependent on the particular circumstances of the system.

EXAMPLE 1A

In this example, the third surface of a 2.2 mm glass substrate is coatedwith approximately 400 Å Ti0₂ followed by approximately 180 Å of ITO andfinally with approximately 195 Å of silver-gold alloy (93% silver/7%gold by weight). The titanium dioxide and ITO are preferably appliedsubstantially to the edge of the glass and the silver alloy ispreferably masked inboard of at least the outboard side of theassociated seal. In at least one embodiment the second surface comprisesa ½ wave (HW) layer of ITO. The associated element reflectance andtransmission model is illustrated FIGS. 48 a and 48 b, lines 4801 a and4801 b respectively. The model reflection is approximately 57% @approximately 550 nm and transmittance is approximately 36.7%.

EXAMPLE 1B

This Example is configured similar to Example 1a except with achrome/metal tab along at least a portion of a perimeter area of thethird surface extending beneath the seal to improve the conductivitybetween an associated clip contact area and the silver alloy. Theappearance remains the same however, the darkening speed is improved.This feature may be applied to a number of the following examples toimprove electrical conductivity from the third surface to the associatedelectrical contacts. As can be seen from FIGS. 48 a and 48 b, thereflectance associated with the element of Example 1a while thetransmission of each is dramatically different; this represents one ofthe advantages of the present invention.

EXAMPLE 1C

Example 1c is configured similar to Example 1a, however, a display areais initially masked and a stack consisting of Cr/Ru is deposited oversubstantially the entire surface, subsequent to removing the mask (i.e.resulting in only the Cr/Ru on the glass in the display area. The Cr/Ruopacifying stack may be replaced by a number of combinations. Thereflectance and transmission results are depicted in FIGS. 48 a and 48 bby lines 4802 a and 4802 b, respectively. The opacifying stackpreferably has a low contrast for both reflectivity and color, relativethe display area. Another advantage in this example is that the metalsgenerally used in the opacifying layer may extend to the edge of theglass to bridge between an associated electrical connection clip and thethird surface silver-gold alloy. The model reflection is approximately56.9% @ approximately 550 nm in the viewing area and approximately 57%reflection in the display region with transmittance <10, <5% preferred,<1% even more preferred, and <0.1% most preferred design goal (thisapplies to all comparable designs) in the viewing area and transmittancein the display region of approximately 36.7%. It should be understoodthat a light sensor may be located behind the “display area” in additionto, or in lieu of, a display or other light source.

EXAMPLE 2A

In this Example, the third surface of a mirror element is coated withapproximately 2000 Å of ITO followed by approximately 50% transmissionchrome and finally with approximately 170 Å of silver-gold alloy.Preferably the ITO and chrome are coated substantially to the edge ofthe glass and the silver alloy is masked inboard of at least theoutboard side of the seal. The Cr thickness is preferably adjusted sothat the ITO plus Cr layer measures 50% transmittance through the backplate only. In at least one embodiment the second surface preferablycomprises a half-wave ITO layer. The reflectance and transmission of theelement is illustrated in FIGS. 49 a-49 d lines 4901 a and 4901 brespectively. The Cr layer may be adjusted (thicker or thinner) toadjust the final transmittance of the transflective element. As the Crlayer is thickened the transmittance will drop, when the Cr layer isthinned the transmittance will increase. An added advantage of the Crlayer is that the stack is relatively color stable for normal vacuumsputter deposition process fluctuations in the base ITO layer. Thephysical thickness of the chrome layer is preferably betweenapproximately 5 Å and 150 Å, more preferably between 20 and 70 Å andmost preferably between 30 and 60 Å. The model reflection isapproximately 57% @ approximately 550 nm and the transmittance isapproximately 21.4%.

EXAMPLE 2B

Example 2b is similar to Example 2a except with chrome/rutheniumcombination stack coated to obtain a transmittance of 50% when measuringthe back plate only (i.e. prior to incorporation in a mirror element).Addition of the Ru layer provides improved stability during curing ofthe epoxy seal. The ratio of the Ru and chrome thickness may be adjustedand there is some design latitude. Chrome is incorporated primarily toimprove the Ru adherence to the ITO. The Ru has preferred bonding to theAg or Ag alloy. Other metal or metals may be placed between the Cr andRu layers so long as the proper material and physical properties aremaintained. The reflectance and transmission characteristics aredepicted in FIG. 49 c, lines 4901 c and 4902 c, respectively.

EXAMPLE 2C

Example 2c is similar to Examples 2a and 2b except a display area isinitially masked and a Cr/Ru (or other opacifier) layer deposited oversubstantially the entire third surface subsequent to removing the mask.Transmission and reflectance results are illustrated in FIGS. 49 a and49 b, lines 4902 a and 4902 b, respectively. The associated advantagesare similar to those of Example 1c.

EXAMPLE 3A

In this Example, the third surface of an EC element is coatedapproximately 400 Å of T_(i)O₂ followed by approximately 180 Å of ITOfollowed by approximately 195 Å of silver and finally with approximately125 Å of IZO-TCO.

This Example is similar to example 1a, the TiO2 and ITO are coatedsubstantially to the edge of the glass and the silver is masked inboardof at least the outboard side of the seal and a layer ofIndium-Zinc-Oxide (IZO) or other TCO is subsequently applied over thesilver as a protective barrier from the EC fluid. Alternatively, theIZO/TCO layer may extend substantially to the edge of the glass. In atleast one embodiment, the second surface preferably comprises ahalf-wave ITO layer. The element reflectivity and transmission isillustrated in FIGS. 50 a and 50 b, lines 5001 a and 5001 b,respectively. The model reflection is approximately 57% @ approximately550 nm and the transmittance is approximately 36%.

EXAMPLE 3B

Example 3b is configured similar to Example 3a except a display area ismasked and a stack consisting of Cr/Ru is deposited over substantiallythe entire unmasked area of the third surface. The Cr/Ru opacifyingstack may be replaced by a number of combinations of materials. Thereflectance and transmission results are depicted in FIGS. 50 a and 50 bby lines 5002 a and 5002 b, respectively. An advantage in this exampleis that the metals generally used in the opacifying layer may extendsubstantially to the edge of the glass and provide a bridge between anassociated electrical contact clip and the silver alloy. Relatedreflectance and transmission measured data is depicted in FIG. 50 c,lines 5001 c. 5002 c, respectively.

EXAMPLE 4A

In this Example, the third surface of an EC element is coated withapproximately 2100 Å of ITO followed by approximately 225 Å of siliconand finally with approximately 70 Å of Ru or Rh.

All of the layers may be coated substantially to the edge of the glass.Alternatively the glass may be processed in sheets and cut subsequentlyinto singles for incorporation into a mirror element. The Ru or Rh layermay be replaced by one of several highly reflective metals or alloys. Inat least one embodiment the second surface is preferably coated withhalf-wave ITO. This example illustrates the advantage of increasedtransmittance at different wavelengths. The base ITO layer may bereplaced having layers with different thicknesses. In some embodimentsit is preferred that the ITO is an odd multiple of ¼ wave. In thesecases the reflectance will be slightly enhanced by the ITO. This effectis diminished somewhat as the ITO gets thicker. The benefit of thethicker ITO is generally lower sheet resistance which will result infaster element darkening times. The model reflection is approximately57% @ approximately 550 nm and the transmittance is approximately 11.4%.The modeled reflectance and transmission is depicted in FIGS. 51 a and51 b, respectively. The measured reflectance and transmission isdepicted in FIG. 51 c, lines 5101 c, 5102 c, respectively.

EXAMPLE 5

In this Example, the third surface of an EC element is coated withapproximately 2100 Å of ITO followed by approximately 50 Å of chromefollowed by approximately 75 Å of Ru and finally, optionally, withapproximately 77 Å of Rh.

All of the layers may be coated substantially to the edge of the glassor the glass may be processed in sheets and subsequently cut intosingles for incorporation into mirror elements. The Ru layer may bereplaced by one of several highly reflective metals or alloys oradditional layer(s) may be added such as rhodium. The metal layers maybe adjusted to obtain a higher or lower reflectivity/transmittancebalance. In at least one embodiment, the second surface is preferablycoated with a HWITO layer. One benefit of the thicker ITO is lower sheetresistance which will result in faster element darkening times. ThickerITO may increase the third surface stack roughness which may result inlower reflectivity. This effect is observed when comparing the modeltransmission and reflectance of FIGS. 52 a and 52 b, respectively to thetransmission and reflectance obtained from the experiments (lines 5201 c1 and 5201 c 2, respectively of FIG. 52 c). The model reflection isapproximately 57% @ approximately 550 nm and the transmittance isapproximately 7.4%.

EXAMPLE 6A Opacifier Layer on Third Surface

In this Example an opacifier layer is incorporated into the thirdsurface coating stack. A base layer stack of approximately 600 Å ofchrome followed by approximately 600 Å of ITO is deposited onto a glasssubstrate either with a display area masked during the depositionprocess of the base layer stack or the base layer stack is subsequentlylaser deleted in the display area. Subsequently layers of approximately700 Å of ITO and (approximately 180 Å of silver-alloy Ag—X where Xindicates the option for an alloy of Ag) are applied. This approach issubstantially opaque in the viewing area and transflective in thedisplay area.

The alloy may be masked relatively far away from the seal to improve thelife of the element in harsh environments. The model reflection isapproximately 52% @ approximately 550 nm and the transmittance isapproximately 41%.

EXAMPLE 6B

Example 6b is similar to Example 6a. In this Example the third surfaceis initially coated with a base layer stack of approximately 600 Å ofchrome followed by approximately 100 Å of ITO followed by approximately500 Å of T_(i)O₂ and finally by approximately 50 Å chrome other than ina display area. Substantially the entire third surface is subsequentlycoated with approximately 150 Å of T_(i)O₂ followed by approximately 500Å of ITO and finally by approximately 180 Å of silver-gold alloy. Themodel reflection is approximately 54% @ approximately 550 nm and thetransmittance is approximately 41%.

An electrochromic mirror, may have limited reflectance (R) if a hightransmittance (T) level is desired or alternatively limitedtransmittance if high reflectivity is required. This may be described bythe relationship R+T+A=1 assuming the absorption (A) remains constant.In some display, or light sensor, mirror applications it may bedesirable to have a high level of transmitted light or (luminance) toadequately view an associated display or transmit adequate light,through the mirror element. Often this results in a mirror with lessthan desirable reflectance.

solutions to deal with the mentioned limitations have been discussed inother examples herein where the thickness of the metal layer or layersare adequate for reflectance in the viewing area and are thinner overthe display area only. Other examples employ layers of differing metalsor coating stacks over the display area in an attempt to match colorand/or reflectivities of the different regions. Often times an abruptchange in reflectivity or color is objectionable to an observer.Referring to FIGS. 55 and 56 a, for example, the boundary (C) betweenthe two regions is abrupt. Region (A) has a higher transmittance thanregion (B). Boundary (C) delineates the two regions. In FIG. 63 theboundary at the start of the transition between high and lowerreflectance region is also abrupt. The slope of the reflectance changeper unit distance approaches infinity as one transitions between theregions.

In at least one embodiment a transition in the metal layer thickness isgradual in manner. A gradual change in reflectance and or transmittancein a transition region is more difficult for the human eye to detect.Two regions still have distinct reflectance and transmittance values,however, the boundary between the two regions is graded. The gradationeliminates the abrupt discontinuity and replaces it with a gradualtransition. The human eye is not as drawn to the interface when it isgraded. The grade may be linear, curvilinear or other forms oftransition illustrated in FIGS. 56 b-56 d. The distance over which thegrade takes place may vary. In at least one embodiment the distance is afunction of the reflectance difference between the two regions. When thereflectance between the two regions is relatively low, the distance ofthe grading may be relatively short. When the reflectance difference islarge, a longer grade may be desired to minimize visibility of thetransition. In at least one embodiment length of the grade is a functionof the application and intended use, observers, lighting, etc.

In at least one embodiment, shown in FIG. 56 e, the transmittance may bereduced to near zero in one or more portions. The reflectance may be thesame or different in other cases described herein. The “stealthy”embodiments described elsewhere herein may be employed to keep thereflectance relatively constant while allowing the transmittance to betuned in various portions of the mirror element as desired.

The present invention is not limited to having two or more regions ofconstant transmittance or reflectance. One embodiment is illustrated inFIG. 56 f. Region B has a relatively low transmittance that may be zero.This may be desired if one of the design goals is to have region B blockthe light coming from objects placed behind the transflective coatedsubstrate. The coating stack may have a gradual transition from region Bvia grade C. Region A may have another gradient within itself. There arepotential benefits to this that will be discussed below.

In certain applications sufficient length may not be available to attaina dual plateau situation. In these cases, it is advantageous to use acontinuous grade across the area where transflective properties aredesired, as illustrated in FIG. 57 a. The change in reflectance isgradual and the benefits of higher transmittance are attained; there isno abrupt interface between the regions.

The grade between the two zones may take on various forms. In thebroadest sense an element may comprise regions of distinct and uniformtransmittance and reflectance. In the examples shown in FIGS. 57 a-57 c,there are not regions of constant reflectance and transmittance. Thesecases have a gradual and continuous change in optical properties.Advantages to this approach are illustrated in FIG. 58.

When a viewer looks at a display through a mirror element or coatedglass substrate there is a continuum of path lengths and angles inrelation to a closer portion of the display relative to a far portion ofthe display. Depending on the orientation of the mirror element display,the size of the element, distance from the observer, etc., the effectiveangle relative of incidence will change. This results in a differentamount of transmittance through the glass at various portions of adisplay area. The different amount of transmittance in turn leads to achange in brightness of the display. When a constant output of lightfrom all regions of the display is desirable the transflective coatingmay be varied to take into account the loss of transmittance arisingfrom the viewing angle and path difference through the glass. If theeffective angle of viewing changes from about 45 degrees to 60 degreesthe transmittance through the glass will vary by about 6%. Thus, havinga graded transflective coating in the region of the display maycompensate somewhat for this effect and therefore can result in a moreequal perceived light intensity across the display.

A graded transition zone may be used for a display such as a rear cameraor a traditional compass temperature display. In some of the “stealthy”examples discussed elsewhere herein a so called “split Ag” stack isprovided where an opacifying layer is placed between two Ag layers tohelp match the appearance between the areas of transflective and opaqueproperties. In another embodiment of a stealthy display an Ag layer isplaced above an opacifying layer. Both of these embodiments may benefitfrom a graded transition between the regions. The opacifying layer or Aglayer or all layers may be graded. In at least one embodiment theopacifying layer may be graded to minimize the abruptness of thetransition between the regions.

Many methods may be employed for varying the material thickness in thelayer or layers to create transition regions, including but not limitedto, masking; motion or speed variations on either the substrate orcoating source; magnetic field variations in a magnetron, or layerreduction techniques such; as ion beam etching as described herein orother suitable means.

FIG. 59 illustrates an example of an electrochromic mirror constructionhaving a back plate 5914 of glass, layer 5972 including a sub layer oftitanium dioxide of approximately 440 Å and a sub layer of ITO of about200 Å, a layer 5978 of 6Au94Ag where one region has a thicknesses ofabout 140 Å another region has a thickness of about 235 Å, and a thirdregion between the first two regions where the thickness graduallytransitions between the two, an electrochromic fluid/gel 5925 having athickness of approximately 140 microns, a layer 5928 of approximately1400 Å of ITO, and a glass plate 5912 of 2.1 mm. The resultingreflectance of the element ranges from about 63% in the majority of themirror to about 44% in the area in front of the display.

A similar electrochromic device to that described above was constructedwhere the thickness of layer 5978 was varied in a manner similarlydescribed and illustrated in FIG. 57 c using a combination of maskingtechniques and magnetic manipulation of the deposition source. Themethod of choice will depend on the exact features required in thefinished element and what processing methods are available. FIGS. 60 and61 depict the corresponding reflectance data as a function of theposition on a mirror. A display is placed behind the region of lowreflectance, high transmittance in this instance.

Another application of graded transitions is in electrochromic elementshaving a second surface reflector that hides the epoxy seal; areflectance and color match between the “ring” and the reflectorpositioned on the third or fourth surfaces may be achieved. The bestmatch is when the reflected intensity of the ring matches the reflectorreflected intensity. In at least one embodiment the reflectance of thereflector is further increased while not altering the ring. This mayoccur because of durability, manufacturing or other considerations. Ameans to maintain the match between the reflector and the ring may beobtained when the reflectance of the reflector is graded as discussedabove. When a gradual change in reflectance occurs, the reflectance ofthe reflector may be tuned to match the reflectance of the ring near thering and then gradually increase moving away from the ring. In thismanner the reflectance in the center of the viewing area is relativelyhigh, as seen in FIG. 62.

In a similar manner the ITO may be gradually changed from the ring areato the center of the viewing area to preserve the thickness rangenecessary for acceptable color while allowing a relatively highreflectance in the center of the element. In this manner, the mirrorwill darken relatively quickly compared to the case where the ITOcoating is relatively thin across the element.

The same concepts may be extended to the metal reflector electrode. Inthis case grading may be employed such that the sheet resistance of thecoating varies gradually with position. This method compliments variousbus configurations and results in faster and more uniform darkening.FIG. 63 illustrates an embodiment of a mirror element in accordance withthe state of the art prior to the present invention.

It should be understood that the detail descriptions provided herein areintended to allow one of ordinary skill in the art to make and use thebest mode of various embodiments of the present invention. In no wayshould these descriptions be construed as limiting the scope of theappending claims. The claims, as well as, each individual claimlimitation shall be construed as encompassing all equivalents.

What is claimed is:
 1. A transflective electro-optic (EO) mirror elementfor use in a vehicular rearview assembly, said transflective EO mirrorelement comprising a first glass substrate having first and secondsurfaces, the first surface corresponding to a front of said rearviewassembly, the second surface carrying a transparentelectrically-conductive layer thereon; a second glass substrate havingthird and fourth surfaces and disposed in a spaced-apart and parallelrelationship with respect to the first substrate such as to form a gapbetween the second and third surfaces opposing one another, the thirdsurface having a thin-film stack thereon that includes a layer oftransparent conductive oxide (TCO) carrying a layer of high-reflectancematerial, wherein a value of sheet resistance of said thin-film stack isless than 6.8 ohms/square, a value of absorbance of said first substratewith the thin-film stack thereon is greater than 12%, a value ofreflectance of said first substrate with the thin-film stack thereon isgreater than 63%, and a value of transmittance of said first substratewith the thin-film stack thereon is greater than 2.5%; and an EO mediumin said gap; wherein values of reflectance, absorbance, transmittance,and color characteristics are measured in light from a D₆₅ standardilluminant, and wherein the high-reflectance material includes amaterial that defines higher reflectance relative to a material, of thethin-film stack, a contribution of which to a sheet resistance of thethin-film stack is the largest.
 2. A transflective EO mirror elementaccording to claim 1, wherein the layer of TCO includes one or more ofITO, F:SnO2, Sb:SnO2, Doped ZnO, and IZO.
 3. A transflective EO mirrorelement according to claim 2, wherein the value of sheet resistance ofsaid thin-film stack is less than 4 Ohms per square.
 4. A transflectiveEO mirror element according to claim 1, wherein said layer of TCO hasoptical thickness greater than ¾ of a wave.
 5. A transflective EO mirrorelement according to claim 1, wherein said layer of TCO has opticalthickness greater than 5/4 of a wave.
 6. A transflective EO mirrorelement according to claim 1, wherein said high-reflectance materialincludes at least one of silver, a silver alloy, chromium, rhodium,ruthenium, rhenium, palladium, platinum, iridium, silicon, asemiconductor material, molybdenum, nickel, nickel-chrome, gold, a goldalloy, and combinations thereof.
 7. A transflective EO mirror elementaccording to claim 6, wherein the semiconductor material includes atleast one of SiGe, InSb, InP, InGa, InAlAs, InAl, InGaAs, HgTe, Ge,GaSb, AlSb, GaAs and AlGaAs.
 8. A transflective EO mirror elementaccording to claim 7 having a transmittance spectrum, within a visibleand near infrared spectral regions, wherein the highest transmittancevalue is at least 1.5 times higher than the lowest transmittance value.9. A transflective EO mirror element according to claim 7, wherein lighttransmitted through said second substrate and said thin-film stack ischaracterized by a C*=√{square root over (a*²+b*²)} value of at least 8,wherein a* and b* are coordinates of a CIELAB chromaticity diagram. 10.A transflective EO mirror element according to claim 6, wherein saidthin-film stack includes a fourth layer disposed under the layer ofhigh-reflectance material, the high-reflectance material includingsilver or silver alloy and the fourth layer including chromium, and thetransflective EO mirror element is characterized by reflectance ofgreater than 55 percent and transmittance of about 21 percent.
 11. Atransflective EO mirror element according to claim 1, wherein saidthin-film stack includes a third layer adjoined to the layer ofhigh-reflectance material.
 12. A transflective EO mirror elementaccording to claim 11, wherein the third layer is disposed under thelayer of high-reflectance material and includes at least one ofchromium, stainless steel, nickel, Inconel, indium, palladium, osmium,tungsten, rhenium, iridium, molybdenum, rhodium, ruthenium, silicon,tantalum, titanium, copper, a platinum group metal, an oxide, and metaloxide.
 13. A transflective EO mirror element according to claim 11,wherein the layer of high reflectance material includes silicon and thethird layer includes ruthenium.
 14. A transflective EO mirror elementaccording to claim 13, wherein said third layer is disposed over thelayer of high-reflectance material, the high-reflectance materialincluding silver or silver alloy, the third layer including achromium-ruthenium bi-layer.
 15. A transflective EO mirror elementaccording to claim 1, wherein a value of transmittance of said firstsubstrate carrying said thin-film stack is greater than 5 percent.
 16. Atransflective EO mirror element according to claim 1, wherein a value oftransmittance of said second substrate with said thin-film stack thereonis greater than 10 percent.
 17. A transflective EO mirror elementaccording to claim 1, wherein a value of reflectance of said secondsubstrate with said thin-film stack thereon is greater than 70 percent.18. A transflective EO mirror element according to claim 1, wherein saidthin-film stack includes a third layer disposed on top of the layer ofhigh-reflectance material, the high-reflectance material includingsilver or silver alloy, and the third layer including at least one ofrhodium, ruthenium, palladium, platinum, nickel, tungsten, tantalum,stainless steel, gold, molybdenum, and alloys thereof
 19. Atransflective EO mirror element according to claim 1, wherein thethin-film stack further comprises a layer of transparent conductiveoxide material disposed in contact with the EO medium.
 20. Atransflective EO mirror element according to claim 19, wherein the TCOincludes indium-tin oxide.
 21. A transflective EO mirror elementaccording to claim 1, wherein a first reflectance value of said secondsubstrate with the thin-film stack thereon measured light incident ontothe third surface towards the fourth surface is higher than a secondreflectance value of said second substrate with the thin-film stackmeasured in light incident from the fourth surface towards the thirdsurface.
 22. A transflective EO mirror element according to claim 1characterized by reflectance of greater than 45%.
 23. A transflective EOmirror element according to claim 1 characterized by reflectance ofgreater than 55%.
 24. A transflective EO mirror element according toclaim 1 characterized by reflectance of greater than 60%.
 25. Atransflective EO mirror element according to claim 1 characterized, inreflection, by neutral color.
 26. A transflective EO mirror elementaccording to claim 1, wherein an auxiliary layer is disposed over thelayer of high-reflectance material, at least one of the layer ofhigh-reflective material and the auxiliary layer including an openingdefining a transflective zone of the transflective EO mirror element inan area of the opening and an opaque zone in an area adjoining the areaof the opening.
 27. A transflective EO mirror element according to claim26, wherein at least one of reflectance value and color of lightreflected by the transflective zone of the transflective EO mirrorelement substantially matches that of light reflected by the opaque zoneof the transflective EO element.
 28. A transflective EO mirror elementaccording to claim 1, wherein a peak-to-valley roughness of a surface ofthe layer of high-reflectance material is less than 150 Angstroms.
 29. Atransflective EO mirror element according to claim 1, wherein apeak-to-valley roughness of a surface of the layer of high-reflectancematerial is less than 50 Angstroms.
 30. An electro-optic (EO) mirrorelement for use in a vehicular rearview assembly, said transflective EOmirror element comprising a first glass substrate having first andsecond surfaces, the first surface corresponding to a front of therearview assembly, the second surface having a first layer oftransparent conductive oxide (TCO) thereon; a second glass substratehaving third and fourth surfaces and disposed in spaced-apart andparallel relationship with respect to the first substrate to form a gapbetween the second and third surface that oppose one another, the thirdsurface carrying a thin-film stack that includes (i) a second layer ofTCO having a sheet resistance of less than 6.8 ohms per square and asurface roughness of less than 200 Angstroms, and (ii) a layer of highreflectance material on top of the second layer of TCO, and an EO mediumin the gap wherein the high-reflectance material includes a materialthat defines higher reflectance as compared to that of the second layerof TCO, and wherein a contribution of the second layer of TCO to a sheetresistance of the thin-film stack is larger than that of any other layerof the thin-film stack.
 31. An EO mirror element according to claim 30,wherein said high-reflectance material includes at least one of silver,a silver alloy, chromium, rhodium, ruthenium, rhenium, palladium,platinum, iridium, silicon, a semiconductor material, molybdenum,nickel, nickel-chrome, gold, a gold alloy, and combinations thereof 32.A transflective EO mirror element according to claim 31, wherein thesemiconductor material includes at least one of SiGe, InSb, InP, InGa,InAlAs, InAl, InGaAs, HgTe, Ge, GaSb, AlSb, GaAs and AlGaAs.
 33. Atransflective EO mirror element according to claim 30, wherein saidthin-film stack includes a third layer adjoined to the layer ofhigh-reflectance material.
 34. A transflective EO mirror elementaccording to claim 33, wherein the third layer is disposed under thelayer of high-reflectance material and includes at least one ofchromium, stainless steel, nickel, Inconel, indium, palladium, osmium,tungsten, rhenium, iridium, molybdenum, rhodium, ruthenium, silicon,tantalum, titanium, copper, a platinum group metal, an oxide, and metaloxide.
 35. A transflective EO mirror element according to claim 33,wherein said third layer is disposed over the layer of high-reflectancematerial, the high-reflectance material including silver or silveralloy, the third layer including a chromium-ruthenium bi-layer.
 36. AnEO mirror element according to claim 30, wherein the layer ofhigh-reflectance material includes a layer of ruthenium.
 37. An EOmirror element according to claim 36 wherein the layer ofhigh-reflectance material includes silicon.
 38. An EO mirror elementaccording to claim 30, wherein a value of absorbance, of said secondsubstrate with the thin-film stack thereon, measured in light from a D₆₅standard illuminant is greater than 12%.
 39. An EO mirror elementaccording to claim 30 wherein a value of reflectance, of said secondsubstrate with the thin-film stack thereon, measured in light from a D₆₅standard illuminant is greater than 63%.
 40. An EO mirror elementaccording to claim 39, characterized by a value of reflectance, measuredin light from a D₆₅ standard illuminant, greater than 50%.
 41. An EOmirror element according to claim 30, wherein a value of transmittance,of said second substrate with the thin-film stack thereon, measured inlight from a D₆₅ standard illuminant is greater than 2.5%.
 42. An EOmirror element according to claim 30, wherein a value of transmittanceof said second substrate with said thin-film stack thereon is greaterthan 10 percent.
 43. An EO mirror element according to claim 30, whereinat least one of the first and second layers of TCO has a thickness ofodd number of quarter waves.
 44. An EO mirror element according to claim30, wherein at least one of the first and second layers includes one ormore of ITO, F:SnO2, Sb:SnO2, Doped ZnO, and IZO.
 45. An EO mirrorelement according to claim 30, characterized by reflectance, measured inlight from a D₆₅ standard illuminant, of greater than 55%.
 46. Atransflective EO mirror element according to claim 30, characterized byreflectance, measured in light from a D₆₅ standard illuminant, ofgreater than 60%.
 47. An electro-optic (EO) mirror element for use in avehicular rearview assembly, said mirror element comprising a firstglass substrate having first and second surfaces; a second glasssubstrate having third and fourth surfaces and disposed in spaced-apartand parallel relationship with respect to the first substrate with thethird and second surfaces being opposite to each other, the secondsubstrate carrying a thin film stack on a surface thereof, the thin-filmstack including a layer of transparent conductive oxide (TCO) carrying ahigh-reflectance coating, wherein a value of sheet resistance of saidthin-films stack is less than 6.8 Ohms per square, and wherein atransmittance value of said first substrate with the thin-film stackthereon is greater than 2.5%; and an EO medium between the second andthird surfaces and, wherein values of reflectance, absorbance, andtransmittance are measured in light from a D₆₅ standard illuminant,wherein the high-reflectance material includes a material that defineshigher reflectance relative to a material, of the thin-film stack, acontribution of which to a sheet resistance of the thin-film stack isthe largest, wherein a value of reflectance of said mirror element inlight incident onto the fourth surface towards the third surface smallerthan a value of reflectance of said mirror element in light incidentonto the first surface towards the second surface.
 48. An EO mirrorelement according to claim 47, wherein said high-reflectance coatingincludes at least one of silver, a silver alloy, chromium, rhodium,ruthenium, rhenium, palladium, platinum, iridium, silicon, asemiconductor material, molybdenum, nickel, nickel-chrome, gold, a goldalloy, and combinations thereof
 49. A transflective EO mirror elementaccording to claim 48, wherein the semiconductor material includes atleast one of SiGe, InSb, InP, InGa, InAlAs, InAl, InGaAs, HgTe, Ge,GaSb, AlSb, GaAs and AlGaAs.
 50. A transflective EO mirror elementaccording to claim 47, wherein said thin-film stack includes a thirdlayer adjoined to the high-reflectance coating.
 51. A transflective EOmirror element according to claim 50, wherein the third layer isdisposed under the layer of high-reflectance material and includes atleast one of chromium, stainless steel, nickel, Inconel, indium,palladium, osmium, tungsten, rhenium, iridium, molybdenum, rhodium,ruthenium, silicon, tantalum, titanium, copper, a platinum group metal,an oxide, and metal oxide.
 52. An EO mirror element according to claim47, wherein the high-reflectance coating includes a layer of ruthenium.53. An EO mirror element according to claim 52, wherein thehigh-reflectance coating includes silicon.
 54. An EO mirror elementaccording to claim 47, wherein a value of absorbance, of said secondsubstrate with the thin-film stack thereon is greater than 12%.
 55. AnEO mirror element according to claim 47 wherein a value of reflectance,of said second substrate with the thin-film stack thereon is greaterthan 63%.
 56. An EO mirror element according to claim 55, characterizedby a value of reflectance greater than 50%.
 57. An EO mirror elementaccording to claim 47, wherein a value of transmittance, of said secondsubstrate with the thin-film stack thereon, is greater than 2.5%.
 58. AnEO mirror element according to claim 47, wherein a value oftransmittance of said second substrate with said thin-film stack thereonis greater than 10 percent.
 59. An EO mirror element according to claim47, wherein the layer of TCO has a thickness of odd number of quarterwaves.
 60. An EO mirror element according to claim 47, wherein the layerof TCO includes one or more of ITO, F:SnO2, Sb:SnO2, doped ZnO, and IZO.61. An EO mirror element according to claim 47, characterized byreflectance of greater than 55%.
 62. A transflective EO mirror elementaccording to claim 47, characterized by reflectance of greater than 60%.